All these are effects, not causes.
The real cause:
This shitcoin was distributed for free to Bitcoin holders, and further airdropped to registered Bitcore holders. Increasing selling pressure in the absence of a use-driven demand.
Byteball and Bitcore are siblings - bottomless shitcoins with interesting technology ideas and absolutely no reason for holding.
PoW mining does not make Bitcore any more valuable - the share of mining reward to existing supply is very low, rational miners don't hold coins below their average cost of mining - they dump them.
Yeah, I am salty about the price...
You stated many good points there, but there are a lot of other PoW coins that did not fall in the price this much! And there are very bad PoW coins that people are still mining and dont dump them this much. I think that btx have their own mining farm with nvidia 1060 cards so they will mine it if noone else does.