* They grew insanely fast for several years in a row.
* They had crazy usage numbers.
* They convinced VCs they would go public at a huge valuation.
* They got a huge buyout offer from Google.
* They IPOed, giving the company a $12B valuation and bringing in billions in cash while giving investors high multiples of their investment.
All of those things are tremendous successes, not worth laughing at. Now from an outside perspective, they're not a traditionally successful company. They're currently worth about 1/4 of their day 2 stock price. They're trying to find a better business model (Groupon Goods?), because their daily deals wasn't cutting it. The company was, in my opinion, a pump-and-dump type of company: not built for the long haul, but for raising the next round of cash.
Laughing at Groupon? I'd be more jealous: they were able to complete a sprint, but so far in the marathon, they're not looking like a company built to last. They look like a company that is using the IPO cash to search for something to sustain themselves, while cutting costs to extend their runway. To say that's "successful" is a bit of a stretch, in my mind. Their success was in hitting all the right metric for a large IPO. Since then, it's been a bit of a dud.