Why are we talking about linear vs. nonlinear development for players drafted 2nd or 3rd? I don't even disagree about your examples. But the discussion is about which prospects are stagnating. I think having a pedestrian, at best, D+1 for a 2OA from a great draft is showing stagnation.
And look, the same applies to everyone. Bedard had high expectations. And he went out there and averaged like 30 points more per 82 than both of the two guys behind him. You can talk about the adjustment from Europe to North America, and I'm not saying it's nonexistent, but a rookie season isn't easy for anyone. How easy do you think it was for Bedard when the media decided that his teammate was having an affair with his mom? It's a challenge for all of them.
I'm not saying Carlsson or Fantilli won't turn into good NHL'ers. They probably will, but I don't think their seasons were what was expected of them. I think more was expected and they had pedestrian seasons. Not disastrous like Slafkovsky the year before, and you're right that development isn't linear. Slafkovsky turned it around. Possible that Carlsson will score 100 points next season, but we're dealing with right now and I think more was expected of Carlsson based off last season.
You're still discounting that they are in their D+1 entering the NHL as 18 year olds. The examples I provided weren't for rookies in general, they were rookies who played in the NHL right out of the draft. Kids like Crosby, Gretzky, Yzerman, Mackinnon, Jagr, Bedard (he had the 14th best D+1 season of all time) are the exceptions not the rule. And I'm not really sure why you're comparing Bedard to Fantilli and Carlsson here. It's well understood that Bedard was a generational draft prospect. The line on Fantilli, Carlsson, and Michkov were that they could go first overall in some but not all years. Like in a more average year with guys like say, Hischier. Obviously expectations for Bedard were going to be higher and it should surprise exactly no one that he performed well as an 18 year old.
That doesn't mean that guys like Fantilli and Carlsson are immune from the challenges of adapting to the NHL that affect everyone. Again, big rookie seasons for 18 year olds are a rarity. In the years since stats started getting recorded there's been exactly 24 players who have scored 50 or more points as 18 year old rookies. Yet you're talking about it like it should be expected of every highly touted second and third overall pick.
And you're conflating emotional challenges with very real transitional realities for players making the jump from Euro pro or tier 2/3 leagues to North American hockey. Sure people making jokes about Bedard's mom is no easy thing for the kid to deal with but that's a very different challenge compared to going from a much larger ice sheet to NA hockey where, especially at the NHL level, the competition is bigger, there is less space to maneuver, the pace of play is much much faster, the incidence of physical contact is much higher, and the games played schedules are much longer.
So focusing on Carlsson, he has to adapt to all those things while still growing into his body and developing his hockey tools while playing top line minutes with guys he has no chemistry with (Killorn who seemed to have chemistry with nobody, and Terry who was an incorrigible puck hog and turnover machine all year). The reality is for every individual Kaprizov, Kucherov, and Laine that finds success jumping from Europe to the NHL, there's 10 other exciting European prospects who can't adapt to the difference between ice sheets and the high level of play and they never amount to anything. Hitting a 43 point pace under the conditions Carlsson faced is not stellar but it's promising because there's a difference between watching a player play and looking at raw stats. Carlsson still needs to work on faceoffs, obviously, and his timing needs work given that, as mentioned, he has less space and time to work with than he used to, but on the flip end, he showed that his hockey IQ and natural game sense can make him adaptable going forward since he showed on many occasions that he has the ability to find lanes and make plays in tight and under heavy pressure. This can only improve as he puts more muscle on his 6'3 frame as he's already fairly strong in terms of puck retention under pressure, the issue is he's been light on his frame and gets knocked over from time to time. As he gets stronger that will be less and less of an issue for him. It's also promising that, even though it's a super small sample size, the one game Carlsson played with Gauthier it appeared like they had far better chemistry together than Carlsson with Killorn and Terry. This is what I mean by qualitative analysis by the way.
Ultimately I don't know who was out there expecting Carlsson to step into the league as an eighteen year old and scorch the league up. If I had to guess I probably would have said 40-50 points considering all the factors I've already discussed. He ended up at around a 43 point prorated pace which would be on the lower end of my estimation, but again that's because I'm not expecting 18 year olds to score more than 50 points in their rookie seasons, particularly if they have to deal with adapting to a different style of hockey while adapting to a higher level of it too. Like I said, generational prospects are exceptions and not the rule and a guy like Laine was an abberation and he hasn't really progressed much past that heater of a 64 point season.
So I guess the conclusion is your belief that he and Fantilli have stagnated are based on your own imagined false equivalency that people saying they could be first overalls in other years equates to "they were expected to have scored 60 or more points as D+1s"
But that brings us back to the Jack Hughes comparison and your reducing Fantilli and Carlsson's potential to just possibly being "good." If we were to employ your logic, we should have looked at his rookie year and determined that he stagnated as a young player and no one should expect him to become an elite player because he couldn't amount to more than just "good" as based on his disappointing rookie year. We'd all proclaim that and all be proven stupid as we watched Hughes end up a hair under 100 points. That's my point when I bring up linear development. Prospects aren't cars. It's not like you draft a Ferrari second overall and if the engine isn't up to par, it's a dud and there's nothing you can do about it other than gut and rebuild the engine. Some prospects hit their stride later than others. It's not like you draft a kid with promise and they either scorch the league as an 18 year old or they're incapable of later greatness. The entire point I'm trying to make is it's entirely too early to bring down expectations on Fantilli and Carlsson's potential cap and it makes no sense to claim they've "stagnated" as prospects just because they didn't have all-timer D+1 seasons. They're still developing and it's their first year developing as NHLers. I'll give you another concession, now that they have a year of NHL play (truncated as both seasons may have been), if you watch the players and observe both on the scoresheet and in the qualitative evaluation of their play that they aren't progressing and growing,
then you can say they've stagnated. But you just can't reliably compare the performance of two fresh faced kids in the NHL as 18 year olds to their play in the NCAA or SHL under any recognized definition of the word "stagnated."
By my observation of both players, both have made meaningful strides in their individual games compared to their draft years, so that's what irritates me about you seemingly only looking at raw stats to draw sweeping and conclusive opinions like this.