Fintech startup Blend recently closed a $130 million funding round with two lead investors, trouncing CFO Marc Greenberg's expectations for one lead and a haul of $75 million to $100 million. Big banks have been turning to fintech startups like Blend that promise to help make cumbersome processes like mortgage lending easier. To win investors over in its latest round, Blend couldn't just pitch a broad vision — it had to produce hard metrics to prove customers would pick and stick with its products.