Motive was any one of the Federal crimes the suit alluded to which elevated the misdemeanors to felonies. You can’t disconnect them and still have a viable suit.
But the motive prohibition only applies as to official acts. For example, in the J6 case, some of the charges relate to things Trump said in his speech. If the speech is (correctly) ruled to be an official act, they cannot try to determine if the reason he said what he did was really because he wanted to win rather than because of his concern for the integrity of the electoral process.
Since the payments were not official acts, they can consider the motive for those acts. Now, there are also issues with using alleged federal crimes as a basis for a state conviction, but that has nothing to do with this SCOTUS decision.