It is true that all these high-growth companies go through major adversity on their way to the top, but this is where most end up failing. Just like every other high-growth company, Snap's valuation is predicated on atypical future results.
Even without adversity they have a tough road ahead. I would posit that there's a good chance the executive team & investors saw the writing on the wall and took the company public to get out before it totally collapsed.
It was a pretty strong signal that Evan & Bobby are primarily money-driven when they took $10M each off the table during the B round. Other notable companies where founders have done this sort of thing have resulted in fast spike-and-collapse results: Foursquare, Zynga, and Groupon.
Zuck didn't take an early multi-million dollar cash-out. The Instagram founders didn't either -- they were living in 1-bedroom apartments a year after the acquisition. Founders who believe in the long-term success of a company don't tend to get rich off a company that has not yet attained either their vision or produce significant wealth for itself. Obviously causation != correlation, but this is a pretty strong signal about the motivations of the founding team.
It's certainly their prerogative to cash out early. I'm not making a moral judgement here. However, as a value investor this is a useful signal for high-growth tech companies. This all sounds incredibly cliche, but I just don't see signals that lead me to believe Evan & Bobby have motivations in the same category as Bezos or Zuck or Jobs. All the signals are that they appear to be looking to get rich to live a life of luxury, not build their life around their company. As a human, I personally would prefer the former. As an investor and employee, I want to put my money and time into companies lead by the later.
[Disclosure: Former Instagram & Facebook employee. I don't currently own any Facebook shares]