There is really not enough information here for us to give any meaningful advice I'm afraid but there are some things I should point out.
First, it would be helpful for you and your mother to learn about canine body language. Whatever led him to growl, then bite, will have been preceded by a lot of him trying to communicate that for some reason, he has been uncomfortable. When a dog bites, it's because he has already given every ”back off” signal he can and the bite is a last resort because he has nothing else left to warn you off with.
These signals could be muscular tension, lip licking, yawning but if you don't see them, and more importantly pay attention to them, he has to keep escalating them - shouting louder if you will - until the bite is all he has left.
Second, the crate should be his safe happy place - so never used for punishment.
I really think you and your mother need someone to observe in person. I realise it is difficult with Covid but this has been going on for two years.