“...a departure from a historical norm in which former presidents tend to avoid openly criticizing their successors.”
That’s because Zero has no class.
... and was elected based on the color of his skin, not the content of his character.
Candidates generally don’t flip the bird at campaign rallies or show off their erections on their private planes either... Obama was always a low class piece of crap...But the press would cover for him... so it didn’t matter.