That's just plain wrong. Trump only had the chance to start a hot war with Iran because he himself had ramped up tensions with Iran to that point; he'd just assassinated Iran's top military commander, getting over a hundred US troops injured in the process. He's been using CIA ops and choking Iranians to death with starvation sanctions with the explicit goal of provoking a civil war in Iran and he's greatly increased US military presence in the region to back up his escalated aggressions. Iran is one of the few areas Biden would actually be less hawkish than Trump.