I don't think it's down to bad luck, but it's the fact that there is an undeniable correlation between being a good dev at a startup and that startup succeeding. It's obviously not the strongest correlation, but it's there. If you have two developers, each about equal, and one was a member of a startup that did well, and one wasn't, it's obvious where the chips are going to fall. I don't think anyone calls that luck, even if they probably should at least be aware it could be bad luck.