But to answer your question more directly, I think the first thing that really hurt Newcastle fans was how he treated club legend Kevin Keegan. Ashley for some unknown reason decided to hire Dennis Wise as some sort of backroom guru despite being vastly underqualified, despite also having failed everywhere as a manager, and having just relegated Leeds in their historically worst season ever, and put Derek Llambias in place as MD, a man who run a disco in London and had never set foot in a business that size, nor had experience of football.
Keegan clashed with both quickly, as both started to interfere and try to make management decisions on his behalf. Keegan is supposed to of had a quite violent meeting with Wise that spilled out of control, the result of which ended with Keegan walking out and eventually suing the club successfully in a multi-million quid unfair dismissal case. The Newcastle fans were outraged a club legend had been forced out by two jokers in the backroom they'd never heard of, but Ashley seemed to side with Llambias (Keegan went for talks to salvage the situation and demanded both were sacked, but Ashley refused).
From there things descended into utter farce. Ashley hired Joe Kinnear, a has been manager who'd been retired a decade who turned up to his press conference seemingly drunk, and who then went through the press assembled insulting them personally, using the C*** word liberally. If you have never seen this, its hilarious. Check below link.
https://www.youtube.com/watch?v=aN4gcNYo7RMKinnear was an embarressement. He didnt even know the player names. He called Charles N'Zogbia... Charles Insomina. In a rant later to the Mirror, again seemingly drunk, he went through a raft of players in his squad and got all their names wrong. He called for instance Yohann Cabaye, the start of the team, Yohann Kebab. Again hearing is believing.
https://www.youtube.com/watch?v=4_s3vBNeTy8Kinnear basically relegated Newcastle, the club hiring another club legend Alan Shearer a couple of games towards the end with the team almost already relegated. Shearer ended up failing, but just like Keegan, the club ended up insulting him by not even letting him know whether he was manager, and Shearer claims he just had to assume Llambias sacked him, because he never got called.
Chris Hughton then became manager, got them promoted, and Ashley sacked him. Another popular figure with the fans, another situation that enflamed them. It basically continued like this for 15 years.
In that time he gave Pardew an unprecedented 8 year deal. He sold all of Newcastle's players, never invested the money back, leading to two relegations. He changed St James Park to the Sports Direct arena....
I could go on and on. Basically at every attempt, Ashley p8sses off the geordie fans. Its almost got the point he trolls them. And he claims he doesnt invest because he wants to sell, but receives bids everyday to sell up and refuses them.
All he wants to do is continually suck the club and asset strip it.