Purely a personal view here but Sunderland - and their rivals Newcastle - had and have this mindset even as top flight clubs.
How many times did we see hostile crowds, season tickets thrown and empty seats at the SoL from the 80th minute on even when they were a PL club? I still enjoy Gary Lineker's jibe on one episode of MOTD - 'Beat the traffic at Sunderland by staying until the end'. Nothing ever seems good enough for them. They want to be a big player and be finishing top half of the PL but there are a host of better financed, better run clubs than them nowadays. Having impressive attendances and selling out away ends does not afford you big club status anymore. You're one of the rest and only from careful management from the top down and a sense of realism, patience and understanding will they perhaps enter that sphere again.
There was once a degree of sympathy from me for their woeful mismanagement at the top but that disappears when you see the treatment of Jack Ross and Lee Johnson from their fanbase. They are constantly angry, arguing for instant change and instant results. Sorry, folks - look around you. You're playing Accrington, Burton and Shrewsbury who have a fraction of the resources but have stability and wise heads keeping them here. You're playing sides you have played in the top flight down here too - Portsmouth, Wigan, Sheffield Wednesday, Ipswich, Bolton, Charlton - you're not the only big gun in League. You're not 'on loan' here. You have to fight for your way back and the unending pressure they put on the club is crippling it.
If I were to become Sunderland manager, I'd use a few hard truths in a Wilder-style. Tell them 'I don't give a toss about your history', this is where you are and this is my plan to get you out of here. Don't like it, see you later. Aim to build from the back and acquire talent in an MAsh/MApp style with a mix of young and sellable assets, seasoned League 1 pros and to balance the books where the average wage for the highest and lowest earners is narrowed to avoid squad discontentment. They don't need Defoe and McGeady. They need the sort of players that Rotherham rely upon and Blackpool acquire for small beer (not Brannagan obvs). You don't need flashiness - some size, some grit, some talent and a fanbase willing to accept that.