They are not comparable.

A league title then relegation is rank failure.

Top 4 and a couple of cups, while not success, is far from rank failure.

Had wenger won the league in the last ten years and then took us to the brink of relegation the following season, he'd have lost his job too.

It is wenger'a consisteny in keeping us ok the top 4 and winning a couple of cups that has kept him in his job.