Cheers for that mate. I think they will have problems filling a 55k capacity stadium every week, especially if they go down. From what I can tell, their support (both numbers wise and atmosphere wise) has been galvanised by Bielsa's arrival and when he goes they could have a problem and might struggle to regularly fill a 37k capacity ER, let alone a 55k one. That said, even if he goes and they go down I don't see a drop-off in attendances to the numbers they were getting in many of those seasons pre-Bielsa and would expect their crowds to hold up reasonably well.
On that last bit, it sounds like they have similar issues with atmosphere and early leavers that we do. On a decent day, they're very good but if they're bailing out of games in the numbers they did at that Brentford game in their first season back in the PL with fans in attendance, then maybe the novelty is wearing off quicker than expected. SSS (Second Season Syndrome) probably isn't helping of course. It's also worth remembering that when Stoke came up in 2008, they were getting loads of plaudits for creating a loud and intimidating atmosphere. And they were certainly loud on our visit there for an early Saturday kick-off in January 2009. Fast forward a few years though and they wanted rid of Pulis, the atmosphere took a significant nosedive, and while there was a brief pick-up under Hughes their atmosphere went to shit again. They're doing quite well in the Championship these days but I see footage of their games and their ground is never anywhere near full, unlike those early Premier League seasons.