How The Future Came To Be (FINALE SPOILERS)

[Powder]

I know we could delve into this in the episode discussion thread, but I figured with all the speculation folks like to do, this particular aspect of the series finale warranted its own thread. What lead to the events that created this wasteland? Who/what/when/where/why?!

We see that a mutagen bomb goes off, presumably in New York City, which turns, as far as we can tell, almost the entire planet into a mutant wasteland. There are no humans left, very few structures/resources. Leonardo is shown to be in the center of the blast radius, pushing his brothers to safety, & taking the brunt of its hellish consequence all alone. Behind him, is what created the blast. To me, that totally looks like a Kraang design, whether it's the bomb or a ship deploying it.

1. If there are no humans left, does that mean it's because they became mutants, or that they just plain died out? We see a bunch of humans become mutants in the flashback, however Casey Jones' skull is 100% that of a human. So he was okay, yeah? Does that mean then that some humans, perhaps those who were in basements or bunkers, for example, weren't exposed, then later died of natural causes or were killed by mutants?

2. Is it possible that the strike was indeed Kraang's doing? They never had their plots 100% tied up, did they? Could Prime have still been around in some capacity? It'd make sense that she/it wanted revenge & as such pulled a caper like this. I don't remember how they ended up. Did they blow up the moon, too, to mess with tides & other earthly processes?

3. If we're to believe this was all going down somewhere in the vicinity of NY, the tri-state area or whatever, what's up with the dominant species gangs? Meerkats (formerly), lizards, honey badgers, they don't exactly run in packs around their neck of the woods. Why weren't they just deformed humanoids or a wide variety of different animals? I guess we can just assume the creative team had to make good use of their 3D resources & as such limited the species count, but even so, why pick those 3 over any other?

4. Was hair growth a side effect of minor mutagen exposure for the turtles? Why Raph/Mikey but not Leo? Did he shave, despite his manic state?

Do you personally believe other mutant homies of the turtles are still kicking at that point? Like Slash/Leatherhead at least? I'd like to think so. Kind of a shame we didn't get to know anyone else's fate, if you ask me.