I don't think the people who were voting were thinking about what a Hamas victory would mean politically in Israel. They probably were thinking at a very micro level, i.e. I have to eat, those Fatah people have been stealing aid money for years and letting us starve; let's try the other guys who are now outside the government and therefore yet untouched by corruption. It's a similar feeling to the "throw the bums out" anti-incumbent dynamic that grips our own electorate once in a while.
Putting myself in their shoes, they see Israel making decisions that make sense to Israel, but make it difficult not only for the Hamas people, but for the non-Hamas people too to survive. By Israel not caring what happens to innocent people, those people over time will radicalize.
Elsewhere, when radicals come to government as "reformers" they are expected to conform and govern responsibly. So should Hamas.
No where else in the world would a country be expected to accept the excuse, sorry about the rockets but you can't retaliate or you might radicalize the populace, when the so-called "moderates" voted the people shooting the rockets into power in the first place!
The solution is for the Palis to demand that their government quit making war on Israel by firing rockets, attacking and kidnapping Israeli troops, all on the land of Israel proper. Not to demand Israel not respond to acts of war coming from the Palis.