Hey i have exactly the same issue.
It can't be my router downloaded Warzone and Cold War without issue, but as soon as i download a game on steam i get a full crash of the wifi, only solution is to reboot or unable reable the wifi card.
I have fiber optic, 500mbps, unlimited, Deco M4, Asus S17 with a mediatek wifi card.
Tried uninstall the wifi card with new drivers and nothing changed.