Spin it any way you like, bottom line is that expecting Marner to "easily" do something he's done once in his entire career is foolish.
I expect he'll be the same player no matter where he plays. Very good to excellent for the regular season and the first few games of the playoffs, then as the games get bigger he gets smaller and smaller. Put him someplace that has no expectations of playoff success to begin with and he'll be loved by the entire fanbase.
I have no idea how you're so sure of this, but I hope you're right.