To be fair I don't think Dyche was underperforming even this season, as he'd done brilliantly to keep in the Premier League for so long (including 7th and 10th place finishes with more than 50 points) in the first place. It seemed inevitable that their lack of spending on transfer fees and more importantly wages for Premier League standards was always going to catch up with them eventually, and that's unlikely to improve under their current owners. It was also a fair assumption that if they were to get relegated, that he'd be the best man to get them promoted again given that he has already done that twice before, and in very impressive ways.
But I certainly wasn't expecting them to pick up 7 points in their next 3 games after sacking him. The players have clearly responded well to hearing a different voice, after being used the same regime for so long. If this change works and keeps them up, fair play to them, they'll have proved me wrong ! It's also reasonable for managers who play more 'cautious' brands of football to face more pressure when results are not good, as bad results plus negative football is never a good combination.
I completely agree that there is often this mentality that smaller clubs should 'stay in their lane' and know their place'. I also remember the outrage when Brighton sacked Hughton in 2019, when they had narrowly survived after ending the season in a disastrous run of form, while playing negative, cautious football in the process. Hughton had done an excellent job there but it was time for a change. They made the change after the end of the season though and they appointed his (highly rated) replacement pretty quickly.