It's unsubstantiated. There were elements in the Nixon Administration and the FBI who desperately tried to deport John Lennon in the Seventies. When the matter was dropped, it's possible to surmise that their sentiments to neutralize him didn't subside and they chose another method or venue to accomplish their goal.
Mark David Chapman was a man with delusions. I'm not saying Manchurian Candidate, but like John Hinckley Jr., his mental status could make him susceptible to suggestion and pliable in the hands of others. Possible, but not probable.