How does raising money -> acquisition work?

Say my goal is just to maximize money and retire early. I have acquaintances who started startups with dumb ideas and have unfinished or mediocre product and still raised $10m, (another raised $25m) and from reputable places somehow. Now they are “in the crunch” and trying to grow the product but it seems they’ve been frozen for a few months. Also, they’ve already received acquisition offers (I’ve been told they’re not good, but they’re there). I don’t know enough about financing in startups and VC to understand how this works, but say they raised $10m in exchange for 12.5% equity at a $80m valuation, and they receive an acquisition offer of $40m. Would they be able to sell and exit, and come away with profit, if some equity owners are okay with devaluing their own shares to sell? Or do they need to raise more than $80m? Also how common is it to “pump and dump” a startup, to just raise money, and exit a year or two later with a few $m in profit from an acquisition?