The answer to this question appears to be that, yes, the FBI did. At any rate, that conclusion follows from this BuzzFeed article.
[S]ome of those informants, acting under the direction of the FBI, played a far larger role than has previously been reported. Working in secret, they did more than just passively observe and report on the actions of the suspects. Instead, they had a hand in nearly every aspect of the alleged plot, starting with its inception. The extent of their involvement raises questions as to whether there would have even been a conspiracy without them.
A longtime government informant from Wisconsin, for example, helped organize a series of meetings around the country where many of the alleged plotters first met one another and the earliest notions of a plan took root, some of those people say. The Wisconsin informant even paid for some hotel rooms and food as an incentive to get people to come.
[A key informant] became so deeply enmeshed in a Michigan militant group that he rose to become its second-in-command, encouraging members to collaborate with other potential suspects and paying for their transportation to meetings. He prodded the alleged mastermind of the kidnapping plot to advance his plan, then baited the trap that led to the arrest. . . .
Last week, the lawyer for one defendant filed a motion that included texts from an FBI agent to a key informant. . .directing him to draw specific people into the conspiracy — potential evidence of entrapment that he said the government “inadvertently disclosed.”
It's now become obvious that it was really an FBI plot all along to fake a kidnapping of Governor Whitmer to smear her opponents. Anyone involved who was not part of the FBI plot was a dupe working at the FBI's direction.