Mitch Marner has a 22-game point streak, Nylander has put up 23 points since November first, John Tavares has 18, and Auston Matthews has 23 in the same time frame. Not only have the four of them been rolling offensively, but defensively they have been much better since the switching of Marner and Nylander as well, as you can see below.
2022/23 5v5 on-ice scoring
Tavares w/ Nylander165:42 6GF 7GA
Matthews w/ Marner234:28 11GF 10GA
Tavares w/ Marner164:55 9GF 4GA
Matthews w/ Nylander190:57 14GF 3GA
Both lines have been far better defensively since Matthews and Nylander and Tavares and Marner were reunited, in particular Matthews' line where they are outscoring opponents by 11 goals at 5-on-5. The swapping of Marner and Nylander has created two top lines that are balanced much better and has allowed Sheldon Keefe more flexibility in terms of matchups.
Lost in the the Nylander/Marner swap is the resurgence of Michael Bunting who has benefitted mightily from Nylander's ability to drive play. Bunting is on his own 8 game point streak currently, as he has been able to simplify his game playing with Nylander. This is the first time Keefe has stuck with these changes for this long and he is finally seeing the reward, but as much as people disliked Mike Babcock, this was one thing he did right during his tenure with the Leafs.