there is no leverage to start this war, so I don't see how you can say that with certainty. (granted, me saying I think teh US or Israel will drop a nuke is similar)
2 completely separate situations.
Trump and Netanyahu illegally started this war because they were under the assumption that all of the behind closed door disdain for Iran would translate into support of the war from the GCC and Europe. The problem for them is Trump's administration is incompetent and Netanyahu is thirsty, so the way they went about it left them on their own.
There is no legitimate, perceived or imaginary justification for either the US or Israel to use a nuclear weapon in Iran. Especially not now with growing war crimes, an obvious quagmire ground invasion scenario, lack of allied support, and what would be permanent damage to the Strait and it's effects on the global economy.