Some people may find that paradox games such as Heart of Iron will crash on windows 10.
According to the steam page, paradox games often require directX 9.0c as the running time.
However, since windows 10 doesn't support directX anymore. And windows 10 pre-install with directX 11. The games can't run properly.
go to https://blog.csdn.net/VBcom/article/details/9140197 and download the DirectX repair
run the application and restart your computer.