As someone not from England who doesn't have that insight: Where does that sense of entitlement from Newcastle fans actually come from? It's something I never really got.
I understand that every club always think they're bigger than they are but they last won the league 100 years ago, haven't won a trophy for over 50 years and apart from two short good spells in the mid 90s and early 00s they haven't really been a consistent top table team either for a prolongued period. I always understood why they wanted Ashley gone and I get that they're a big club in the North and have a long tradition - but the way their fans talk always reminded me of Liverpool - thing is, Liverpool fans for all their delusion actually had reasonable reference points of being great "once".
They've always been well supported, most football clubs can't match their numbers in that regard. Even when they dropped down to the championship they were getting 40k+ every week. Of course that doesn't translate to trophies and as you said their trophy laden years were a long time ago, but I don't necessarily think the supporters demand trophies, but rather a team that can shake off the malaise off the Mike Ashley era and to make it fun to go to the ground again.
Before Ashley you had some good Newcastle sides with good players during the spells you mentioned, you had Keegan's lot with the likes of Ginola, Beardsley, Shearer, Ferdinand pushing for the title with elite players, and you had Bobby Robson's spell with Shearer scoring for fun, and while the supporting cast wasn't as strong there was still good players there with the likes of Gary Speed, Given, Solano, Bellamy and young talent like Dyer and Jenas. Other than that one freak season under Pardew (with some great players but sandwiched between a 12th and 16th place finish), there's been very little excitement for the supporters, there hasn't been a single top half finish (outside of the time they got relegated and won the championship) and the football has often been pretty crap.
The managers since the takeover have been really uninspiring
A long past his best Keegan
Allardyce
Joe fecking Kinnear
Pardew
Mclaren
Benitez
Bruce
I don't think Bruce got a fair crack and he didn't deserve the abuse he got, but I honestly understand why the Newcastle supporters didn't want him. His sides aren't particularly fun to watch, he'd managed Sunderland, it was an appointment that completely ignored how the supporters felt. I support a far smaller side and I'd be sad if Steve Bruce was made manager of my club.
This isn't directed at you as I understand the entitlement question was over why they think their club is bigger than it is rather than other factors, but I think it's less about trophies and more about just wanting to be excited about watching your side. I can accept the fact that it's unlikely my club will win any important trophies, but I do want to be entertained when I go to the games.