With the current arms race with drones, missiles, hypersonic missiles, etc... I think Israel is worried that Iran will begin handing these weapons out to their proxies in Syria, Lebanon, Gaza, and escalate the war.
Iran's drone strike against Saudi Arabia's top oil refinery really highlighted that.
I think ensuring that no deal is better than the current format of the JCPOA. At least in the current situation, they can strike at Iran's weapons program to slow it down, and that there are no major inflows of money.
Personally, I think they'd be open to a new JCPOA that includes broader weapons controls.
It seems both sides are throwing threats around and it seems unfair to only mention Iran’s threats.
https://m.dw.com/en/israel-threatens-iran-over-nuclear-resea...
https://apnews.com/article/joe-biden-israel-iran-iran-nuclea...
Country 1: Has actually threatened multiple times of wiping Country 2 off the map, all the while developing advanced military capabilities and sometimes unveiling them with writings on them of wiping Country 1 off.
Country 2: Has been threatening (and delivering) consequences to Country 1 over nuclear research and other offensive activities they have undertaken.
If that's unfair, then it is also unfair to leave out the fact that the Iranian government has murdered innocent US citizens and funded organizations that seek to murder large numbers of innocent US civilians. We should also mention the two countries differing views on religious freedom and women's rights, or even their differing views on the others right to exist.
Israel is built on the suffering of the Palestinians, taking their land and homes by force in the 1940's, but why didn't Iran take those displaced people in if they were so concerned about them? Or any other of the loudly protesting states that surround Israel? The answer is that the Mullahs only really care about holding on to the power they have, and just like the elite in the US like to use racism to distract from wealth inequality, so too do the Mullahs use Israel to distract Iranians from the fact that Iranian government isn't actually very good at its job of providing a peaceful, prosperous life of freedom for it's citizens.
It seems a real pity that such a wonderful people like the Persians must live under a feudal, fundamentalist religious dictatorship in the 21st century. That must really suck.
My guess is that if there is ever going to be an Islamic Reformation, it will happen in the US or Iran, and it will make the Arab Spring look like a blip on the radar, and it will be wonderful.
But then again, in 2016 we recently proved that 40% of Americans have a good chance of walking out of Star Wars believing that Darth Vader was the good guy. So what do I know?
I am certain that nuclear weapons or not, Israel considers Iran enemy #1 and a real threat to be dealt with. A stronger Iran (via sanctions relief) is not in their interest.