According to the Warriors team site, Hendrix was let go to make room for Monta.
It is doubtful that he would have made a difference. His college numbers suggested he was worth the gamble, but he was having trouble staying on the floor in the NBDL due to foul trouble. It is probably the case that he was not NBA material any time in the near future and any talk of using him as a bruiser specialist ignores that the team has much, much more pressing needs in order to become a real basketball team again. Good teams can afford that. Bad teams have more pressing needs. Still, it looks like yet another bust move. I suspect that cutting him off a non guaranteed rookie min was easier to stomach than eating Marcus Williams's larger contract for the rest of the season.
Is there a more poorly managed roster in the league right now?