While I agree that Hainan was the best of the mainland airlines, it wasn't exactly consistent. Hainan and the entire HNA group wasn't, and isn't, exactly the financially healthiest company on the planet. It was epically loss making - I think they acruued close to 100b in debt before the Chinese government and CCP intervened. Last month they just completed the transfer of their entire core Aviation segment to a steel company (Fangda, one of their biggest investors) under duress allfter officially going bankrupt in Jan 2021. That segment was comprised of ~10 Chinese airlines and substantial stakes in several foreign airlines, including Azul (~25%). Think Evergrande, but aviation - the rest of the conglomerate is undergoing a GE style breakup.
Either way, Given the lack of an open skies agreement between the US and China, the air routes authority that Hainan holds is actually quite valuable, pending diplomatic squabbling. Boston was by far the US city Hainan serviced with the greatest frequency (9x weekly between Shanghai and Beijing). And given their proposals to relaunch in 2020, and prepandemic proposals to upguage, I suspect profitable. Either way, it's a market with demand so someone will probably fly it again soon.