The floor board wasn't loose. These floors are designed to have some give to them so the players joints don't absorb the full shock like if they laid them directly on top of concrete. If anything, that floor made it possible for Bacot to play as well as he did. All NBA floors do that same thing.
My guess is that it was his already severely sprained ankle and the shoes he was wearing that led to him rolling his ankle. They had a guard roll his ankle in those same shoes.
From the court manufacturer:
https://www.espn.com/mens-college-b...r-armando-bacot-was-injured-says-manufacturer