I have been led to believe for 30 years now that my mom was banging santa behind my dad's back and I could never figure out why everyone was nonchalant about the whole thing
Why did you believe this for so long?
I think I know the answer since my mom always used to go to santa's place.
I get that this realization is really shocking, but I feel like it was a little too long for you to believe in something like this. If you were a kid when this happened, then they were perhaps just trying to play a little joke on you. Please don't hate your mom over this.
It's all lies, nothing is real.
Ask your mom if what others have been saying about her is true. Don't wait and rely on gossip, go see for yourself. Either way, let your mom know others are saying about her, and if false, defend her against the accusations.