They probably would have stuck with him until the end of the season if he'd been even slightly amenable to trying something a bit different. It wasn't an option as soon as he went nuclear in the press conferences.
It wasn't a "zig-zag in policy" for his bosses to step in and tell him something had to change, but his reaction to that made his position completely untenable.
I also don't think we'll find out anything about Amorim from how well the interim does. They could be complete shite, but it doesn't change anything about Amorim's underperformance.