alt Hacker NewsThe way I've heard it is that later investors collude (descriptive, academic term, not value judgment) with founders via liquidation preferences, dilution, etc., and effectively wipe out all common shareholders (particularly employees) and all earlier rounds, and then give the founders some additional terms to compensate them specifically. How exactly that works, what they're giving the founders, and how this isn't hugely illegal are all details that I don't understand. I put a top-level comment asking exactly that.
That's exactly the approach. Seen many deals where the (remaining) founders get a big slice of new vesting options or reverse vesting shares as part of a recap or semi-distressed round.
Nothing illegal about it when the company needs the money, just one investor can write the terms they want, and the founders are on board with the plan.