Was there possibly politics involved in the choice of who to go after? Maybe?
You can stop your search there
There are literaly only a single handful of coins that stand a chance of not being classed as a secuity under according the SEC. Bitcoin is so far the only one that they have definitely ruled on as being a commodity.
If you are really interested in the details then go investigate all the crap that the SEC put LBRY though over the last 5-6 years. Do this, no don't do this, do that, no don't do that, provide this, ok here it is, no we mean this, no we mean that...
People expect me to link to a single proof, LOL
The SEC were determinded to screw over LBRY and they did it, whatever it took. In the end you can't blame LBRY for giving up, they got crushed.