Actually, some of our sackings don't even come after "just a few bad results" either.
Take Redknapp. Yes, he hitched his skirts up at the FA for the England job, but I don't hold that against him. An old school guy like Harry, would see being England manager as the pinnacle of his career.
Once it became apparent they weren't going to give it to him though, why sack him? He had us performing well, while playing attractive attacking football.
I didn't think Mourinho was a good fit for Spurs, and the football we played under him made my eyes bleed, but to sack him on the eve of a cup final is just bizarre. Especially as one of the justifications for bringing him in was that he was a winner.
To be honest I think Levy sometimes has the same mindset as a lot of fans. Always looking for the shiny new manager, or transfer rather than being patient and building for the future, with what we've got.
Most of the most successful clubs, stick with a manager for a decent period of time, or they build a structure so that when a manager leaves, the new one can (ahem...) slot right in.
Levy seems to prefer a scattergun approach, and I think ultimately it's holding us back.