I don’t think that’ll come to pass.
When all is said and done, Russia and the USA will stand by and let the Iranians and Israelis blow each other to kingdom come, and issue sternly worded memorandums regarding restraint. There’s an old saying which applies to the realpolitik concept; No one let’s themselves get killed for an ally.
But the time it’s all settled, Tehran, Tel Aviv, Qom and Jerusalem will all bear a remarkable resemblance to Hiroshima and Nagasaki (that depends on how many nukes the Iranians can not only manufacture/assemble, but actually deliver....nukes are pretty useless if you don’t have an adequate delivery system). Though of course, in a nuclear exchange between the two, I can safely say Iran will come out the worse.
Each Iranian citizen will be killed twice, whereas each Israeli will be killed only once.
However the entire land of Israel will become unusable for a while (from months to decades, depending on the weapon.) In Iran only spots around former cities will be contaminated. Iran has a lot of land; most of Iranians, in rural areas, will never even see the nuclear flash. Which means Iran will rebuild (with mullahs being taken care of in the war,) but Israel will disappear from the map, just as the guy promised. Once the Israeli survivors leave (for the USA, Europe, Russia) they will not be too eager to return.