over 2 years ago - AndrewT - Direct link
I don't know why this is happening to you, it's not at all a known issue, on Mac or in general.

If you revert to a pre-3.0 patch does it run again?

Our similar game Crusader Kings 2 is free to play on Steam now, does it run or have the same problem?  
over 2 years ago - AndrewT - Direct link
It is hard to see what could cause this to these two games on your machine. There is of course no general problem with them on Macs! Both work fine on my iMac for instance.

The big difference I see with my machine is I'm on MacOS 11.6 . Have you not updated from 10 for some particular reason or problem?

I ask because I don't really have anything else to suggest!