We need more information obviously.
If it was a professionalism thing behind the scenes, then I can't really blame them. Even though they have let some of the most unprofessional shit slide from other fighters, they are the employer after all, and can choose to let you go if you are hard to work with.
If it was based on his fight style, AND if what he said was accurate, that they told him he needs to wrestle less, then that is a pretty bad sign about the direction the UFC is heading. The UFC directly attempting to influence fights like that is wild.
He was 23, undefeated, with plenty of years before he would even hit his prime. Hopefully, more information comes out.