A very trite comparison. Ike and Harry both loved America. Neither one was a pervert personally or would have thrown their lot on with deviant men who want to chop their penis off and nominated one as asst Sec of health. Both would have been repelled by Buttgig kissing another man on stage. Both would have been sickened at molesting their own daughter like Biden did. Neither would have thought an 8 year old who should be allowed to decide to medically try to change sexes. Both would have been sickened at abortion, and especially secret abortions in middle school and high school hidden from the parents. Neither though communism and Marx were virtues. Both were honorable Army men, Truman in WWI and Ike in WWII.
There was so little distance between Truman and Ike that there really was very little reason they couldn’t be friendly after the election was settled.
My point remains - newly-minted ex-presidents' aren't ipso facto besties.