couple reasons, I'll try to be straightforward and unbiased. years ago, under Obama, Iran and America agreed to a deal about Iran not developing any nuclear capabilities in exchange for America kinda chilling out wrt them. In Trump's first term, he got rid of that agreement, so Iran went back to developing nuclear power. Additionally, Trump campaigned heavily on not starting new wars, and now he is starting a war by stepping in to help Israel, who without question were the aggressors here.