If I can take a guess...

Recruiters are over-excited sometimes. The recruiter told you that you passed. The recruiter told you that you should expect an offer. The recruiter asked for and checked your references.

The hiring manager may have said very little to this recruiter to encourage this. We don't know whether it was "we're going to hire him" or "he's ok let's talk to a few more people".

So there may be a disconnect between Stripe and the agency they use to hire.