In the event that the AI bubble doesn't burst, Stripe needs to have a stake in whatever's coming. They have time to explore and pursue specific strategies, but they just needed to make some big and compatible buy.

In this particular case, OpenRouter represents a M x N bridging and enhancement layer much like Stripe themselves, and so must address a lot of parallel technical, dealmaking, accounting, and legal challenges.

It may not be obvious on the surface because they seem to be working in such different domain, but they have to address a lot of the same problems in comparable ways and that makes it a pretty darn good fit.