John Mearsheimer argues that Israel and the United States previously stopped the 12-day war with Iran because they realized they could not defend themselves effectively.
Israel was overwhelmed by Iranian ballistic missiles, and the US burned through about 25% of its THAAD missile stockpile - an unsustainable risk to US national security. Israel's defensive position today is no better, which explains why any potential new attack on Iran would be carried out by the US alone, with Israel trying to stay on the sidelines to avoid retaliation.
The same constraints that halted a planned January 14 strike still exist: US generals say a decisive victory is impossible, Netanyahu does not want a war, and Iran has clearly warned that any US attack will trigger full retaliation against Israel, US bases in the region, and by closing the Strait of Hormuz.