He was used a tool. Remember this was a Title 1
FISA. That means anyone Page came in contact with, physically, electronically or otherwise, could be put under intense surveillance to include all forms of communication and actions. Also, the people they connected to could come under surveillance. It is meant to uncover a whole spy/terrorist network. I am sure the FBI, NSA, etc. have every word that came out of Trump’s mouth, fingers, etc. as well as his whole team, funders, etc.
Yes. He was a tool. But not a plant. A plant generally means he was undercover. I don’t think the way they handled him supports that conclusion.