Trump said ‘we must abandon the failed policy of nation building and regime change’ in 2016. So what changed?

Barely an hour after the first U.S. and Israeli missiles struck Iran, President Donald Trump made clear he hoped for regime change. “Now is the time to seize control of your destiny,” he told the Iranian people in a video. “This is the moment for action. Do not let it pass.”

Doesn’t sound complicated. After all, with Iran’s fundamentally unpopular government weakened by fierce airstrikes, some of its top leaders dead or missing and Washington signaling support, how hard could it be to overthrow a repressive regime?