I don't like Chauncey Billups being placed on leave.
The crimes he is accused of have nothing to do with basketball (poker) and it is not even clear he has done anything wrong. It just an accusation at this point.
This is punishment before guilt.
It's usually done a) if the allegations are serious and the evidence against the accused is strong; b) if the accused continuing to do their job becomes difficult due to the accusations against them and c) so the accused can focus solely on their legal defense rather than worrying about coaching or playing. Also, the NBA being a private league, has its own rules that govern how to impose discipline on people accused of a crime. Many athletes have been suspended or put on leave for crimes that have nothing to do with their sport like rape, domestic violence, theft, robbery, etc. it's just how that individual league or team chooses to handle things.
That said, organizations need to balance the need to suspend based on what I mentioned above, with the due process rights of the accused, unless it is something they all signed up for, which appears to be in the case of the CBA. Here is the section of the 2023 CBA regarding criminal conduct:
(click to enlarge)

Not sure if this covers coaches.