The new owner may be regret was buying a club with a high price even another club out there (championship division) has a lower price than Newcastle. I'm not sure they can repair it by buying another player or changing a coach, because as I know there's a lot to fix the club not just buying anything. The new owner must look at Chelsea and Manchester city how to succeed, if doesn't Newcastle will be like another club, QPR and Monaco.
1.The new owners of Newcastle are so rich that they wouldn't care if Newcastle goes to Championship next season.
2.Even if Newcastle goes to Championship,they might return to the Premier League in 2023.
AFAIK,there was a big prize for the team,that wins Championship.It was 150 million pounds,if I remember this correctly.This might cover some of the costs.Such large sum should be enough for buying several world class players.
3.AFAIK,the new owners of Newcastle don't care about the football club only.They have some business interests in Newcastle and they want to expand their real estate business in that town.
Chelsea and Man City weren't successful right away,after Abramovich and the Arab billionaires arrived.They had to wait for a year or two.
Newcastle will be fine in the long term.