They didn't start spying on Trump in 2015 or 2016...they'd been spying on him for years because he had the cojones to call out obama's unfitness and disqualifying birth place to be POTUS.
Fusion GPS was not hired to research Trump, the intelligence community was already doing surveillance and spy operations. The intelligence community needed Fusion GPS to give them a plausible justification for already existing surveillance and spy operations.
Fusion-GPS gave the Obama administration the justification they needed for a FISA warrant with the Steele Dossier. Ultimately thats why the Steele Dossier is so important; without it, the DOJ and FBI are naked with their surveillance and database abuse.
Imo, according to what’s been outted so far, and assuming it’s all legit, the dossier as “insurance” finally makes sense to me.
The Steele Dossier “insurance” didn’t get trotted out until immediately *after* the Italian plant job failed.
So, it’s looking now like the Italian plant job was plan A and the dossier was the fallback plan B.