> One reason might be the share price has collapsed and he has no confidence in it coming back (pretty scandalous if he's the CEO!)

From looking at the historical prices, it was down from $450 to $410 from a month ago, but still quite a bit from $235 six months ago, which is not anything close to what I'd consider "collapsed". Of course, he might have expected to continue going down, but that's going to be hard to measure in the short term given that announcements like this tend to affect the price directly in the short term (so far down to $338 today, close to double the loss of the entire previous month, although it seems far too soon to draw any conclusions).

Not that I think I'm saying anything that has any sort of bias, but it's probably reasonable in case anyone happens to read this and be suspicious: I did work at MongoDB for around five years (but haven't worked there for nearly as long), and from that stint I did have a sizable amount of shares, although as of last year I no longer hold any (for reasons completely unrelated to any personal opinions of the company; I had procrastinated way too much on making any sort of decision about how much to hold onto and for how long, so when my wife and I were buying a house, I decided it was time to just liquidate it and put it towards that instead).