Someone (possibly, as nothing here is certain) mined most of this worthless "NFTs". Maybe out of passion, maybe hoping to sell them to idiots, maybe just to spam Bitcoin's blockchain.

That's it. That all the conclusions to be had here.

The whole thing is a big nothing.

Idiots duped to pay for this stuff raised the floor for price of blockchain space from artificially low (due to still low adoption) to a more reasonable one (reflecting the value of global replicated censorship-resistant database). It doesn't change much in a great scheme of things. Some Bitcoin users are annoyed that Bitcoin transactions aren't nearly free as they used to, but it was always just a matter of time.