Exactly, they should be rational just like our secular politicians.
"As a Christian growing up in Sunday school, I was taught from the Bible, ‘Those who bless Israel will be blessed, and those who curse Israel will be cursed.’ And from my perspective, I’d rather be on the blessing side of things.”
- Ted Cruz, a U.S. senator
"There is a reason the first time I shook Netanyahu's hand, I didn't wash it until I could touch the heads of my children."
- Randy Fine, a U.S. congressman
And of course, there's the President of the United States who's known to be completely rational.
Iran has shown itself a rational actor time and time again by not escalating against continued provocation by Israel and the US, knowing that to do so would be to enter a conflict it can’t win. That’s not the behavior of an irrational actor who’s willing to fight whatever the cost, even total annihilation (which would be what happened if Iran nuked the US/Israel).
They may be religious fanatics, but they’re not idiots.
It’s not a justification, obviously. But it is a (partial) explanation. Israel wanted to keep sweeping the Palestinian issue under the rug, and Hamas and its sponsors were not going to allow that.