Enemies who become best friends

The coverage of the Queen's death and in particular the walk about by William, Kate, Harry and Meghan has triggered a few things for me.
My husband is one of three boys. For many years the two wives of my husband's brothers did not get on at all and were very hostile to each other. In the early days their differences came nearly to blows with lots of nasty threats on occasion. It went back years as we all were brought up in the same town and new each other at school. I was never involved and remained friends with both. I tend to be quiet and would never get in a fight but they are both much more firey and aggressive. A few years ago our mother in law passed and because we have quite a big house and garden we hosted the wake. At the time I thought I was doing the right thing and did my best to host everyone. Everyone was happy to start with but it seems that in this process I upset both of my sisters in law by inviting someone neither of them don't like. As a result they both pretty much stopped talking to me and became the best of friends. I can not believe how tow people who used to be sworn enemies are now best friends and I am public enemy number one. both there husbands have told me I didnt do anything that was out of order. They are pretty intimidating together and I feel most uncomfortable now in the family. Any one has anything similar? I don't understand it at all.