That's really the problem. You can't definitively say Pittsburgh won those cups "as a direct result of the trade". It's certainly possible that they would not have won without him, but it's also possible that they would have won without him. It can't be proven either way. In exactly the same way, if the Leafs win the Cup a couple of times in the next three years, you can't say for sure whether it was because of the trade, or in spite of it.
It's probably a pretty safe bet that the Leafs would not have won, and would not be as good now, if they had not made the trade. But that's about as close to certain as anyone can be.
Bottom line is that it is all speculation. Which is fine, but I think anyone who "knows" who won the trade is just fooling themselves.
Absolutely hilarious, this take.
When the Bruins won the cup the year that they drafted Seguin, it was parroted all over the place that the Bruins embarrassed the Leafs in the trade because they went on to win the Cup.
It didn't matter at all that Seguin barely played in the playoffs, his ring was a sure tell sign that he was a winner and that we had acquired a loser.
Now, all these years later, a player who ought to have won the Conn Smythe in one run and was a major contributor in the next can be said to only possibly have had an impact on whether the team won or not.