AFAIK, major browser vendors trust any Certification Authority that follows the Baseline Requirements of the CA/Browser Forum.

https://cabforum.org/working-groups/server/baseline-requirem...

> why trust the others and not Achmed?

Because, "trust us". Seriously, Google, Microsoft, Cloudfare, etc. at the same level as Achmed. The only thing Achmed lacks is marketing.

See comment 13.

He's too honest