Kim doesn’t have much of a choice.
President Trump has given him two options:
1. Comply and denuclearize.
2. Become a pile of rubble like Hiroshima looked like at one time.
President Trump essentially patted him on the back and said “come on son, let me lead you to a good and happy life, all you have to do is become civilized, and I’ll help you do it”. “It will be the greatest!”
“Kim doesn’t have much of a choice.”
there’s also the issue of probable major Chinese pressure of one sort or another, as well as the issue that the Nork economy (such as it is) may be on the verge of total collapse.
One of the biggest, and most unusual, provisions in the initial agreement is that the U.S. guarantees Kim Jong Un’s regime, which tells me that Rocket Boy literally fears for his survival for whatever reason, and it could easily be an internal reason as much as anything.