Federal records show that Stefan K. Halper has been paid $928,800 by the Federal Government since 2012 on four separate "research projects"— Jacob Wohl (@JacobAWohl) March 26, 2018
The FBI would be unlikely to have had enough criminal cases relating to people in Great Britain, where Halper was located, to spend that kind of money. The likely answer is Hapler was doing work for the CIA. That would mean the initial contact may have been a CIA operation launched by John Brennan. The CIA is strictly prohibited from spying on Americans except under certain circumstances and it requires senior approval from several people.
So, either the FBI is lying about when they started their investigation, and why, or they handed off the initial investigation to the CIA because they didn't have enough to launch an investigation on their own. Either way, the Steele Dossier seems to be the real reason the investigation got launched. If the CIA was involved, it would have required the approval of CIA Director John Brennan, DNI James Clapper and Attorney General Loretta Lynch or, alternately, John Brennan went rogue. This likely goes to the highest levels of the Obama White House, perhaps even Obama himself.
As a side note, what's up with the leaking of Halper's name and involvement by the deep state? They are certainly trying to get the initial spin on this spying as something innocuous since it was going to come out eventually. However, I think the main spin is to portray Halper as an FBI informant and hide the CIA involvement because that opens a huge new can of worms.
Note: Edited to correct information about Papadopoulos bar conversation.