Carter Page had not been under continuous investigation since 2013. At that time, Mr. Page became aware that he was being recruited by Russian agents. He did not hide the fact, but rather he went to the FBI and cooperated in a sting operation that resulted in the exposure of the agents.
The relevant thing about Page is that he was a KNOWN entity to the FBI, and thus he made a convenient stooge for the FBI conspirators, since they knew from his dealings with them that they use these facts to lend credence to their false narrative. They knew they could use Page to get to Trump and other senior campaign members. The object of the Page surveillance was not Page, but Trump.
Thank you. That makes sense