One of the great problems we have as people, especially smart people who did well in school, is that we expect success to be the result of cleverness. We put faith in _a crafty plan that is bound to work_. This is not wise. And, since the people you meet in elevators believe the same thing, they will be asking you for _the stupid thing that made it fail_. But I know, and by the time you finish reading these books you will as well, that the thing you did wrong may have been nothing.
This is not what one generally tells people that fail. And, goodness knows, many more things fail because people did something wrong than 'you were just unfortunate'. So in general, analysing your failures in an extremely self-critical way, in order to learn from your mistakes is a beneficial activity. What you aren't told, alas, is that sometimes the answer is _nothing_. And beating yourself over the head for not being able to find out what you did wrong is not helpful if there is nothing there to find.
I am in no way competing in your area, and have a bit of a problem understanding what "social advertising ecosystem trending toward openness" actually means, but for my money if you want to shut people up about your failure, there is nothing surer than saying we needed XXX amount of revenue by quarter Y, we only had YYY, and we couldn't get another round of financing because the market continued to be uncertain. Techies, who generally want a technical fix, tend to shut up at this point. Of course if your problem is that it is the financial people who want to rip open your wounds and comment on what is inside, then your pitch may be the cat's meow. :-) Whatever works.
And you have to get up again, and start the whole damn thing over. Which you may have to force yourself to these days, but I promise you is worth it. But, after reading these books, and learning all about hindsight bias -- there is one question I would leave you with. Did you, in charting the business direction of your company, leave enough room for different possibilities for success, or were you stuck with a 'make-it-or-break-it' fragile plan that either had to work or you were all dead? Because your post did not make it clear.
Make-it-or-Break-its are often a good strategy, because if you are going to fail, you want to do so quickly so you can get up and do something else as soon as it is clear that this is not it. But it's not the strategy for something you put your heart and soul into.
And something in your writing made it clear to me that you are hurting right now. Been there. Done that. Deeply sympathise and wish things were different, and that we could all succeed with the things we love.