Depends on the product, depends on the potential market size, depends on the founders, etc.

And you can definitely have traction and an initial revenue stream without having product-market fit in a meaningful way. You can survive for years on a large-enough group of savvy early adopters (and get funding based on that initial enthusiasm), but if you don't cross the chasm, your revenue stays flat.

Well, they got into YC in an era where funding available to YC companies was basically infinite. Plus they had nonzero sales and an early graph that probably looked good. What VC could say no to that? (Keep in mind “spray and pray YC” is probably a top quartile VC strategy.) Getting into YC post ~2012 basically makes VC funding an afterthought. So the interesting question is what made them attractive to YC. (I’m not questioning, just clarifying.)

Edit: also there are tons of companies that get insane amounts of funding on total punts, with future failure obvious. (Just go trolling through AngelList, you’ll find plenty.) Thinking any one thing is truly necessary to get VC funding is a wildly incorrect mental model.

Product market fit is a pretty undefined term and people interpret it differently; you see companies dying after several rounds of funding for not being able to build a successful business. Usually companies raise the first round of funding (seed) with a prototype or an idea.