In the end, a tough job with that club and crowd. He hasn't been great, but the expectations were always difficult, even with the spending. PL spending is so high and top heavy that Villa can spend a lot and still not be very good. Let's face it. If Stevie turned things around, and they got 9th, would people be that impressed? But on the flip, how much can he really achieve there?
It's a tough business for young British coaches in the PL because there aren't enough borderline CL/EL teams around with reasonable expectations to manage and build. The Top 6 (and even outside of it) usually want the biggest names, so you end up with teams like West Ham, Villa, Leicester, and the like being the best options. You get the occasional European run, but that's not always enough to convince.
The step up is just massive. Graham Potter is a great coach, but the question marks are around if he can handle big egos, constantly losing players to international breaks, and mid-week European games. It just doesn't allow for the amount of "coaching time" he can get at Brighton. Klopp's always mentioned the lack of opportunities to work on things given fixture congestion, and that's a part of the challenge of a non-European coach going to a team that demands European football. Rodgers hasn't exactly been able to handle that either, despite outperforming with Leicester for years.
German coaches are in vogue, but that's also due to their league being very competitive beyond Bayern. Both Klopp and Tuchel coached Mainz in Europe (although I think Klopp's was the Fair Play entry) for a bit. Both were able to manage multiple competitions at Dortmund. They were no strangers to the Champions League when they left Bundesliga. Julian Nagelsmann finished 4th with Hoffenheim, lost to us in the CL qualifiers and had a poor EL campaign, but then qualified for CL again before coaching in the CL at Leipzig. It didn't work out for Marco Rose after coaching in the CL with Gladbach as his Dortmund tenure was no good, but it shows a variety of young coaches getting CL experience. You're hardly going to get this at West Ham, Villa, and the like.
Stevie's European experience with Rangers is a plus, but he'd been better off going to a Bayer Leverkusen type team (good young talent with CL qualification ability) than a Villa, but as we know, it's hard for English/British managers to go abroad with the language issues as well.
The best you can hope for is the Lampard route (Chelsea sacked so many managers he ended up high on their list) or the Rodgers route (given an opportunity by Liverpool perhaps earlier than typical and then continuing to build a managerial CV), but even then it's hard. Maybe the Arteta route if there's a good number 2 that could get a chance (but even then that was a stretch by Arsenal).
Clubs like Dortmund, Leverkusen, Leipzig, Gladbach, etc can't go and hire Conte or Ancelotti or whatever. But when clubs like Everton are hiring Ancelotti, Spurs hiring Mourinho and Conte, Villa fans demanding Poch, etc, top clubs are rarely going to take a chance on a Steve Cooper (awesome player development), Graham Potter, or the like. Stevie has the reputation and strong track record at the start of his managerial career which could give him more opportunities, but big-spending Villa probably wasn't the right choice. But then again, what PL team would've been?