Everything was Spire's fault, that damn hooligan. There is no chance that anyone else did anything to contribute to the downfall. Anyone.
Seriously though, it's been a while and I think you've had more than enough time to reflect on the situation, yet this the conclusion you've come to? Shouldn't a project leader take responsibility for fixing the faults in his team? If Spire was such a problem, then removing him should have resolved everything, yes? It seems however that conflict continued, which should have been a red flag that something else was awry. Perhaps I'm wrong and don't have enough insight to truly say that, but I do know that there were other major issues before Spire even joined the team. Trailer 3 was delayed many times (which may have been from very explainable delays, but the probability of these coincidentally happening just before the trailer's release are low enough for me to reasonably doubt this,) threads were deleted and restarted because of too much drama, and constructive crticism was mistaken for attacks. However, you say that your ONLY problem as the project's leader was letting Spire join the team. That's unlikely, and I'm sure other members were to blame as well for internal conflict.
I hate to throw all of this out there, but this is not intended as some sort of attack towards you or the project. Rather, I think that if you honestly want to achieve your goal of completing this project and releasing it, you will have to rethink how you're going about this. Maybe projects don't need leaders after all, just several components each adding something else to the table. Maybe you could make it more of a collaboration than a "leader and members" situation. Having each person make what they want to make and having it incorporated somehow, even that could work. That gets rid of the feeling that you're being commanded to do something you're not interested in, too.
That's something for you to consider, though. Perhaps you really only made one mistake as a project leader, and that lead to the downfall of the project. Whatever you do, I guess we'll see how that turns out.