This is the first year Team Skyneos riders didn't have to fake being tired on an HC climb, and their most genetically gifted rider won (not the guys who decided to become the world's greatest climbers later in life). Weird season.
Leadership certainly can be an incentive. Don't know his contract details, but wonder if he's making more now. Often the case when a prominent rider leaves a team for a leadership role.
Seemingly if riders are on a program, they would know a great many details about how that program was applied. Not perfectly, and they're not doctors, but they have to know what "stuff" works. So he doesn't "know" what the results will be–if he was on a program at Sky, he may well believe it can be replicated elsewhere.
And again, if he's leaving for more money, it may not matter that much if he thinks he's going to be more successful or have the same success. Gotta feed the family first. Cycling doesn't last that long, and for a lot of athletes, you get what you can get while you can get it.
Also possible that he doesn't think Ineos are getting the air cover from above which they may certainly have been getting under the previous regime. At which point some potential advantages of staying are gone.
The idea that they have some magic potion isn't one I adhere to. Other explanations seem to comport more with the facts on the ground, IMO.
The idea that because one got out, if follows that none were suppressed isn't logical.
Beyond that, there is the obvious that the timing coincides fairly well with Uncle Cookson heading out the door.