they have an infinite war chest and building windsurf/cursor isn't the hard part, building a brand and sales environment around it is. why risk failing the execution and losing focus when you can just buy one with momentum?
it's also a bit of multiple arbitrage in terms of what seriously addressing the developer market means for their valuation, they likely recoup the 3b instantly.
Sometimes it almost seems like the idea that LLMs are capable of instantly creating real, maintainable software is vastly overblown to inflate valuations...