I think he did explain it: Most coins have a centralized development team who are focused on increasing the coin's value. It's a classic investment no different than a startup.
Right now everyone is guessing why exactly the SEC considers most of the top 10 coins to be securities, except Bitcoin, with Ethereum apparently in limbo. Most importantly, it leaves companies guessing whether they'll have to wage a bankrupting 50-million-dollar lawsuit against the SEC to try to defend themselves if they launch a coin they believe not to be a security, but that the SEC later classifies as one through their opaque reasoning process.
I mentioned it in a comment above, but the SEC needs to release something like a 10-step process for determining whether a certain crypto is a security. Something that's clear enough that a company's lawyers can apply it to their products to determine without a doubt whether they are in compliance with the law.
To me, that sounds like a centralized team employing centralized decision making.
The vast number of users, or at least, those who run their own node, choose to run a forked version of the client software that activated a contentious upgrade (the upgrade was Segregated Witness).
Only after the fact, this code was merged into the Core branch.
That's incorrect. The code was merged into the Core branch first. The protocol change was initiated by the developers, not by the users.
Exactly the same way you fork a non-security. Security is a legal designation, not a description of how a particular asset is implemented (in a forkable structure like a blockchain).
> What is the common enterprise when forking a PoW chain?
The developers/promoters of the fork, potentially.