This is all because Apple is moving away from dependence on Intel chips, no other reason. This was a long time in coming.

https://appleinsider.com/articles/19/07/24/why-apples-macs-can-now-ditch-intel-x86

There are a number of good reasons to do so. They have been telling developers to update for years, it is the fault of developers if they still haven't updated. In my case there were no apps that were a problem for me that weren't updated soon after the new OS came out.