It's hard to judge from thousands of miles away. Plus no one knew that the first half of the Greek 2nd tier season would be postponed due to Covid, and I don't remember any official news that Elliot turned down a Nix contract - but this does now shape as a classic case of a young player who would have been better advised to stay and try for 2-3 seasons as an A League regular first.
Aka Singh, Cacace etc.
Elliot will have a right to be annoyed if it's Popa bailing on Xanthi, and not the coach being sacked.
Ange Postecoglou has a good chapter in his book, about his volatile time coaching a 3rd Division Greek side. He fell out with club management and left after only about 6 months.