It is not the case that the ultra-right fringe parties like Jewish Power had governing power for decades. It's a parliamentary system, weirdos get elected to the Knesset, but the governing authorities --- at least prior to Netanyahu, and even during Sharon's time! --- were normies, not neo-Kahanist terrorists. It's easy to find lots and lots of political analysis about why this has happened, much of it having to do with the probability that Netanyahu could wind up imprisoned (for things having nothing to do with Gaza) once he fails to assemble a governing coalition.

See also: https://news.ycombinator.com/item?id=40421217

This dynamic – a political leader trying to run away from justice – has, historically been a very common way in which states fail; which is why a lot of people who pay close attention to such things are very concerned about the state of US democracy.