Sorry to hear this but unfortunately it happens, including in amateur choirs and orchestras, in fact in any club/society/group, which is where my experience mostly sits. I could regale you with tales going back decades… but even in the last few months I’ve walked away from a group due to stupid behaviour. At 64 I’ve zero tolerance of stupid behaviour and I won’t waste my time on such stuff.
The word ‘empathy’ is over-used, but it is what is lacking here. To mix metaphors, some people are just tone deaf. Ultimately, it’s selfishness (people are too quick to use the word ‘narcissist’ these days, which is more extreme) they’ve seen what they think is an ‘opportunity’ and jumped to make it happen without thinking through the issues and consequences.
Unfortunately, this kind of stuff happens, which can shake you as it causes you to lose trust in people. I’ve had two very bad experiences over the years as well as all the small things that happen. The two big ones were very upsetting as I’d given years of my time to both groups.
All we can do is try to learn from it and move on. As someone who has only discovered in the last three years that they are mildly autistic, it does explain some of my difficulties in understanding the behaviour of others. Doesn’t justify it though.
Hopefully other things will come along.
On the plus side, the world of any specialist activity is small and word gets around…
Good luck.