Offset language (basically allowing the team to void all his guarantees if he's punished by the league for any reason). It's very rare for teams to cave on this, but Jacksonville notably did for Lawrence this year. The Jets have never caved on this and maintain a stance that they never will because if they do it for 1 player it could open the door to every other draft pick they have in the future pushing for it and saying "well Wilson got it, why can't I?" Wilson looks at it and is probably thinking Lawrence didn't have offset language and why should his guaranteed money be at the mercy of a ridiculous league that can screw players over as they see fit at times.
Most notable hold out due to this was Joey Bosa with the Chargers, he held out well into training camp I believe. Don't remember the exact resolution but I think the Chargers upped his upfront signing bonus in exchange for him agreeing to have the offset language in the contract.
Theres HS and college players that develop CTE. He very well could have developed it.
That said, I think it's a combo of emotional immaturity and bitterness/resentment over his mothers death. Also some narcissistic poo kinda like DeAngelo.
At the end of the day you are a grown ass man, act like one.
All that said, KB was one of my favorite players and I'm still disappointed and sad that it didn't work out.
What could've been...
I'll always wonder where we would've gone as a franchise had KB not torn his ACL that preseason and then came off the rails after losing his mom. He was emerging as a dominant WR. Instead, he veered off the path, got lazy, and that laziness directly led to Cam's career altering shoulder injury then he blamed everyone else for his problems.