Humans are blitzkrieging the troposphere. Nothing could hope to evolve fast enough except fungi and bacteria I guess

Just give it another million years or so.

Humans have only been dominant for a few thousand years. Give it like a million for enough evolution to happen and then ask this question again.

Before: All phyla differentiated but all the creatures are soft and blobby and sort of unremarkable
After: All of a sudden there's trilobites everywhere, they can see and some of them hunt, and all creatures everywhere suddenly have all this armor and mobility and a lot of them have spikes

I don't really know (even enough to talk about what might be the competing theories), but it seems like it fits and it doesn't seem all that farfetched. That said, it kind of seems like all the scientists think me and Andrew Parker are wrong though, so IDK.

(Also - I didn't know about this before as it's semi-new, but apparently Anomalocaris also had eyes and hunted, so star power of the trilobites aside maybe those guys were involved as well. I have to say though the timing of the way it's written in Wikipedia makes a little more sense if the sequencing is: Cambrian explosion -> some species turn into predators, as opposed to the other way around)

What humans are doing to the natural world right now is a global extinction event (not much different from has happened a handful of times). It's happening too fast for anything to adapt to except in the most short-term emergency ways. Mostly stuff is just dying.

If we stay around for millions of years doing this same thing then I would expect the biosphere to develop defenses and then rebound into a new equilibrium with defense measures included against what we tend to do to it. Even that outcome wouldn't really be another Cambrian explosion though, because everything before it was so universally blobby and unremarkable. That is actually exactly why I like this theory -- the clear lack of a certain type of selection pressure before the explosion happened is as much as part of the theory (there must have been something missing from the threat matrix that suddenly arrived, and what was that thing?) as what things looked like after the Cambrian.

It is happening now but evolution takes a long time. If there were a ton of adaptations that happened in the next 10,000 years, that would be incredibly fast on an evolutionary timescale