I think cheating is very common. I was with someone I loved, would have done anything for and he left me and was declaring his love for someone else the next day. Obviously he was seeing her behind my back. My boyfriend before him was going through a divorce because his wife had cheated.
My sister met her husband when they were both with other people. My fathers first wife cheated on him.
I’ve seen a particular colleague cheat twice on his girlfriend.
It’s just very common in my opinion. I’m currently single but whosever I date next then I wouldn’t be shocked if I found out if they were a cheater.