When President Trump tweeted that he and his associates had been wiretapped by President Obama, he misspoke. He and his associates had been "air-tapped," i.e., been subjected to electronic surveillance by the NSA and who knows who else in the Intelligence and law-enforcement community.
It is not uncommon for eager beavers within the Executive Branch to think they can skirt the law and, at the same time, give the President "plausible denial" which, IMHO rarely, if ever, works. I cite the instance when President Reagan told his WH staff, to include Lt. Colonel Oliver North: "Don’t let the Contras starve," or words to that effect. North, et al, went on to violate the Boland Amendment and the rest is history.
The NSA sweeps up virtually all electronic communications as metadata. If some agency of government with the necessary authority asks to have access to certain portions of what the NSA has swept up, they can ask for it based on concerns of foreign involvement or in suspected cases of criminal activity. Permission from a FISA Court would be needed for foreign involvement and a DOJ request would be needed where criminal activity is suspected.
With regard to Candidate Trump and President-Elect Trump, it appears that both types of requests were made. On top of that, just three days prior to the end of his term, President Obama approved the dissemination of raw electronic sweep data to 16 additional agencies ( well beyond the normal very limited distribution of such data ),
There is a vast difference between "raw data " and finished "intelligence." The latter is a product which has been subjected to careful review and analysis using multiple sources . Once you start spreading raw data around it takes on a life it can take on a life if its own, and if you couple that with the massive distribution that Obama ordered three days before he left office it is relatively easy to leak with not much fear of being found out.
Either with the knowledge of President Obama or not, the objective was an attempt to support the DNC narrative that the presidential election was stolen by the Russians for the benefit of the Trump campaign.
I have no idea how all this will play out except to say that President Trump’s imprecise tweet has been vindicated if not wholly at least in part. Last evening, other than Fox, no mention of Trump’s vindication on major newscasts. Par for the course as the mainstream media is now the heart and soul of the Left . "