There could be any number of reasons why the game crashed, but I'll give you a small list of things you can check to see if it solves your issue:
Verify the files' integrity on Steam. It's a bit long, but any file with issues will be redownloaded, which could help if you are experiencing crashes.
Try to lower the Graphics, you could be in an area of the game that demands too much from your computer. Playing the game in a smaller resolution can also help.
We also know that Solasta has trouble running at over 60 frames per second. You can force the game to render 60 or fewer frames per second in the Graphics Settings, it usually helps players who experience crashes.
If nothing helped, you can send us a DxDiag by email, as well as a save file where the crashes occur, we'll take a look!