I genuinely do not know why this happens and what makes it happen

MHS_2003​  Please go through the list of known fixes for that error again, just in case something changed since you last posted in that thread.

[CURRENT ISSUE] Sims 4 Failed to Launch Game | EA Forums - 12561664

And you do need to restart your computer after you get this error and before trying again.

If none of those help, please post a new dxdiag.