We're not talking about the top 2 lines though...we are talking about the top line.
Knoblauch was playing MCDavid and Draisaitl together (especially in the series against Florida) and he did that a lot because the team doesnt have the depth to play them (as a default) on their own lines when they are chasing a game (or in that case) a series.
So we have to be clear on what it is we are talking about here.
If this team had legitimate depth then the need to play McDavid and Draisaitl on the same line wouldnt be a major factor like it is now.
If this team had legitimate depth then having McDavid and Draisaitl on seperate lines would be the go to strategy in every game because that would make this team much harder to defend.
When the opposing team has to play 2 sets of dmen and a minimum of 2 lines against the Oilers top 2 lines that is a much more difficult task and it relys on tehor team depth.
Teams that win the SC do so because they have legitimate depth in their lineup...on D and at forward.
He played them on the same line because Drai couldn't run his own line due to being severely injured, he could barely move in the latter half of the Dallas series and beyond so he needed to be sheltered.
I don't know why you're not acknowledging that the depth didn't score enough.
Here are the goals in that series from non-McDrai lines...
Game 3 - Broberg, Foegele, McLeod (and btw, McDrai had 0 goals and 3 points combined in the first 3 games)
Game 4 - Holloway scored twice, Janmark, Henrique, McLeod and Nurse all scored.
Game 5 - That was a McDavid game but Brown also scored and it was a big one to set the tone in that game
Game 6 - Henrique, Foegele, McLeod, Nurse
Game 7 - Janmark (only goal of the game)
That's a lot of depth guys on the scoresheet. The Oilers lost that series, and the Cup, because they got hardly anything from their top guys in the losses and they were outgoalied in a few of the games with Game 7 being the most notable one.
Even in the playoffs as a whole, Henrique had 4 goals, 7 points and was +3
Janmark had 4 goals, 8 points and was a +6
Brown had 2 goals, 6 points in 19 games and was a +4.
All huge parts of a historically good PK as well
McLeod was poor especially in the Florida series but he scored some goals, Holloway was good, Foegele was really good in the Florida series.
The depth did their part and were especially instrumental in the last two series.