It’s 6% of world-wide turnover, not EU revenue. The neat part about turnover is that you can’t play shenanigans with accounting. It’s very unlikely to be the full 6% though and they will want to keep some headroom for escalation and even more egregious cases.

But yes this is absolutely “drive a company bankrupt” kind of territory and that’s precisely the intention. Either Twitter shapes up, leaves the EU market, or gets fined into non-existence.