It's succinctly explained in the article:
> Supporting QWACs will mean that browsers will have to support providers that issue them without independently vetting their security practices.
> Supporting QWACs will mean that browsers will have to support providers that issue them without independently vetting their security practices.
Think like EV-Certs, but now with more legally binding power cause you don't get them from some random private company but the government. Though admittedly that legal power is more of a thing when signing documents.