And any way, it's Trump's distraction tweets just gave people like Lindsay Graham a chance to go for it:
The president does not have the unilateral authority to order a wiretap on suspected foreign spies operating inside the US, experts say. Doing so would be a federal crime that would implicate career civil servants and necessitate a huge cover-up. Rather, law enforcement and intelligence agencies wishing to monitor signal intelligence they deem relevant to an investigation - in this case, Russia's interference in the 2016 election - must obtain a warrant from the Foreign Intelligence Surveillance Court.
So Trump then ordered them to look at the accusations, based on one media article, and someone like Graham is happy to use it and won't let go off it. Naturally Trump wants now to move away from the direct accusation on Obama ordering it to a more general approach, that there was an investigation.
Which naturally there is, as the FBI among other services concluded that the Russians had been active in the elections.