None of the arms you listed are pitching opening day because all of them are recovering from injury, right? Keep going down that list of highest AAV pitchers and it reads alot like a 60 day IL right now. Ohtani, Cole, Strasburg (he's retired due to injury but still making $35m a season for a few more years). Many of these same guys are Boras clients, too.
Snell is getting less in AAV than these guys and didn't get close to a similar longterm 9 figure deal because, frankly, he carries a very similar injury risk at 31 and teams have either learned their lesson or already have too many arms that aren't healthy taking up huge swaths of payroll space. Even the biggest market teams have only so much room to pay veteran starters to get injured as they advance into their 30s.