[2021] Crash During Launch

In the game launcher please set Display mode to windowed.

IF that doesn't help, Install ALL these Microsoft modules:

Download Microsoft Visual C++ 2010 SP1 Redistributable Package (x86) from Official Microsoft Download Center

www.microsoft.com

Download Microsoft Visual C++ 2010 SP1 Redistributable Package (x64) from Official Microsoft Download Center

www.microsoft.com

Download Microsoft Visual C++ 2015 Redistributable Update 3 RC from Official Microsoft Download Center

www.microsoft.com

Download DirectX End-User Runtimes (June 2010) from Official Microsoft Download Center

www.microsoft.com (run dxsetup.exe after extracting from this download)

THEN go here:

The latest supported Visual C++ downloads

This article lists the download links for the latest versions of Visual C++. support.microsoft.com And run the x86 and x64 installers there.

Add CK3.exe to the exceptions list of your antivirus app; ESPECIALLY if you have Windows Defender, add it to the Ransomware "Apps Allowed Through" list.

If those don't help:
DXDIAG is a program you run from the Windows search box on the task bar. After running it will open a window and start collecting info with a progress bar in the lower-left corner. When it completes click the 'save all information' button and save it to a file then attach that file here.

Please attach your Documents/Paradox Interactive/CK3/pdx_settings.txt .
From your Documents/Paradox Interactive/CK3/logs/ folder, attach system.log , error.log  

Your AMD video driver is from 2015, I'm sure that is the issue here.

- uninstall it with this tool:
https://support.amd.com/en-us/kb-articles/Pages/AMD-Clean-Uninstall-Utility.aspx - reboot
- install the very latest from here:
http://support.amd.com/en-us/download - reboot again

All the best!  

Is it that the launcher doesn't run? Or it runs but won't start the game?

In this folder are some .log files:
C:/users//AppData/Local/Paradox Interactive/launcher-v2/
Please attach them here.  

Your launcher has not been reinstalled since 2019 so i think we should do that:

- exit the Steam app entirely
- uninstall Paradox Launcher v2 from the Windows "Apps and features" utility, if still present.

Delete the following folders if still present:

- C:/users//AppData/Local/Programs/Paradox Interactive/
- C:/users//AppData/Local/Paradox Interactive/
- C:/users//AppData/Roaming/Paradox Interactive/launcher-v2/
To see the AppData folder you'll need to enable View Hidden Items in File Explorer.

- run steam.exe as the Windows Admin user

- run the game from the PLAY button in Steam

IF that doesn't help, in this folder are some .log files:
C:/users//AppData/Local/Paradox Interactive/launcher-v2/
Please attach them here.  

Those logs look okay actually. What launcher version do you see? Current is 2021.5.1  

Please set all these files to run as the Windows Admin user:

ck3.exe (in the Steam CK3/binaries/ folder)
dowser.exe (in the Steam CK3/launcher/ folder)
C:/users//AppData/Local/Programs/Paradox Interactive/launcher-v2.2021.5.1/paradox launcher.exe
C:/users//AppData/Local/Programs/Paradox Interactive/bootstrapper-v2.exe

Good luck!  

Sorry to have been unclear, I'm not saying you should manually run those files as that can never work. Rather, go into their properties-compatibility and set them to run as Admin all the time, then just launch the game from PLAY in Steam as normal.