Hard to "Decommit" when you've signed a letter of intent.
Kinda like telling the commanding officer you have changed your mind about going to Vietnam after signing up.
They changed the rule on LOIs a few years ago. In the distant past if you signed you had to attend or sit out a year. Now if the coach you signed with leaves you can get out of the LOI and sign with another school. I’m hoping our new coach rerecruits him.
As of December 2021 here is the answer given by the official LOI NCAA page:
Question: Is an NLI binding if the coach of my sport leaves the institution? NCAA Answer : Yes. The NLI you signed with an institution remains binding if the coach who recruited you leaves the institution with which you signed. When you sign a NLI you sign with an institution and not with a coach or specific team.
(My comments) - Most every AD will give a release if the coach leaves, but it must be asked for with a specific NLI Release form and be signed by the institution. The athlete then may sign another NLI with another school.