This transition was in the works for some time. President Trump simply waited for an opportune time to make a change that was predicted weeks ago.
The switch is an obvious godsend for Israel. The Zionist state has pushed for the United States to use its considerable military strength to not only take out Iran's supposed nuclear program, but also reduce the country to rubble the way it did in 2002 in Iraq.
Iran doesn't have a nuclear program. Both Israel and the United States know this. The long-standing accusation is merely a smoke screen for an effort to devastate that country—and Lebanon and Syria as well.
The evidence is everywhere Iran doesn't have a nuclear weapons program—from a 2007 assessment by US intelligence agencies to a National Intelligence Estimate in 2012 which concluded there "is no hard evidence that Iran has decided to build a nuclear bomb." In fact, even Israeli intelligence admitted no such program exists and hasn't since at least 2003.