Did you try verifying local files? In the Steam library, right click on Divinity Original Sin and select Properties, switch to the Local Files tab and then click on the 'Verify Integrity of Game Cache...' button.
Are you shutting down all non-essential programs (especially anti-virus) before starting the game?
Try browsing to the '..\Documents\Larian Studios' folder and renaming the 'Divinity Original Sin' subfolder.
This folder contains the saved games, configuration files and a level cache folder. Deleting or renaming it will get the game to recreate it on startup; playing the game from a different Windows user account would effectively do the same thing.
If that allows D:OS to start, create a new profile and exit, then move your current saves from the renamed folder to the newly created profile's savegames folder.
If it doesn't help, then delete the new folder, and rename your original back again.
Crash on startup [Solved]