Presumably they got well compensated for their time and effort. That's about the best you can expect at a large company. You're working on the company's products and priorities and getting paid to do so. What they choose to do with it is up to them.
The founders know of (or can easily research) Google’s track record with products and they knew the risk going into this acquisition. Probably an unpopular opinion but the time and effort was compensated as part of the acquisition.
The counterpoint to this is that individuals can decide if they want their firm to be acquired or not or to stay around after it has been acquired. I don’t mean to put blame or shame on said folks, it requires a lot of careful thinking and self-inquiry and attention to one’s emotions and body to weigh said decisions well; which is hard for many reasons.
