Neither the game nor the launcher changed recently, so I can only guess something else has changed on your system to cause this to those two unrelated apps (game and launcher). Quite what I'm not sure; a Windows, driver, or antivirus update perhaps.
What exactly happens when you run stellaris.exe directly from File Explorer? What do you see on the screen?
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 here your Documents/Paradox Interactive/Stellaris/settings.txt and pdx_settings.txt .
From your Documents/Paradox Interactive/Stellaris/logs/ folder, attach here system.log , error.log , exceptions.log