Nailed it.
The thing is that he finally put money into the club but even with all the money he spent, the club was so bare of quality that they could patch it over. They bought to many players with potential when they needed players for the now and they completely failed to do much about the biggest problem with the team defense. Add to that poor choice of coach and taking too long to fire said coach plus plenty of bad luck with injuries and you get relegated. I mean seriously I saw an article a couple months ago that said Newcastle made up 11% of the injury time in the entire Premier League. How many teams lose both their starting goalies to season ending knee injuries? Although keeper has been the least of our worries. Elliot was player of the season until getting injured and Darlow has done well since coming in. Also Dummett missing so many games has really hurt us. He is absolute crap going forward (cause he is a centerback being played at right back) but our defense is so much better with him. But luck doesn't excuse the number of poor choices to personal in the upper offices he has made or the lack of investment previous to this season.
There is the quality in the club to straight back up even losing players. I believe we will if we keep Benitez but with the Everton job open, I doubt we will keep him. The buzz seems to be that he will stay if he gets full control of transfers. I hope they give him control partly so he will stay and partly because well he can't do worse then Carr and Charnley have done.