First: Trusting Israel to keep another in nation "in check" is a laughable position... but anyway

Second: I wonder if there isn't more to the desperation to keep Iran, and other "outsider" nations, from developing nukes.

There's a line of thinking, supported by evidence, that nuclear bombs were fake at the beginning and could still be impossible now. Early demonstration footage of test nuclear explosions has been obviously faked (miniature models being "blown up", impossible camera angles, footage splicing etc) and the aftermath of cities that got "nuked" in Japan bears a striking resemblance to a mass fire bombing campaign, like what happened in Dresden. Witness testimony, at the time reported in mainstream press but forgotten about now, has people sheltering in the basement of wooden houses, and surviving, and not experiencing and deadly nuclear illness when they emerged from their hiding place. Only the wooden buildings were completely destroyed, back when the majority of buildings there were wooden, so it looked devastating. However concrete buildings remained standing, if scorched, and right at the supposed "ground zero" too...

Israel's desperation to keep Iran from developing nuclear weapons could actually be about preventing them from fully realising that Israel doesn't really have nukes, nor does America or any other nation...