Example# 63726 of where Trump is an immature, vindictive and cruel person.
James Clapper, Obama's Director of National Security, recently participated in a program where people can sponsor the training of bomb sniffing dogs in support of national security. Clapper is an 84 year old widower who lost his wife 2 years ago. His wife, Susan also worked in national security and was a volunteer with local animal shelters. Via his sponsorship, Clapper was able to name the dog after his late wife. The dog completed training and they hold a "graduation" ceremony before the dog is placed in service.
Clapper was looking forward to attending the graduation ceremony. He received a call from the training group that he was barred from attending due to a exec order from Trump. He's not allowed to attend. It's unknown if Trump specifically banned him due to this event, or there is an overriding exec order that bars Obama and Biden's officials from attending federal events. It's possible that it's the latter and an overeager MAGA type, with power for the first time in his life, gleefully barred Clapper.