I doubt there is any law anywhere prohibiting a millionaire or billionaire from moving themselves and their families to a new place and living a middle class lifestyle under a new name.
Advertising one's wealth is a signal for "I seek validation" and "Please appreciate me"/"Be my friend because I am wealthy"
I doubt anyone is actually stopping Bob from quitting his job, moving to a new country, and living a quaint lifestyle.
Personally, I've up and moved and gone to live in a tent, just to see what it was like and essentially test myself and test the lifestyle of a vagabond.
It really showed me that, as a man, for the most part: you have no worth outside of what you provide for others. Men are expected to provide something for their community-- that is the basis of their social status: competencies (i.e. capable of productive things) and contributions.
There are plenty of rich people who are completely unknown.
The inside of their house is a bit better decorated, and if they fly first class to a private resort, how are the neighbors going to know?
Wise people avoid the hedonic treadmill (https://en.wikipedia.org/wiki/Hedonic_treadmill), independent of their level of wealth.
The thing that makes it simple is that all the things Bob has are purely unnecessary. So if Bob feels overburdened by the task of securing them, then the simple solution is to jettison them.
in other words, don't be a billionaire. However Bob has evidently decided to keep being a billionaire which means he has to maintain and review stolen property etc.
His wikipedia page documents how he and his family have disowned his granddaughter for revealing family secrets in an interview. So.. yeah, he probably does.
You can bet he has kidnapping insurance on his family, too.
I can solve this problem for Bob.
Live a more modest life and not have 10 homes with a million things in them. Maybe stick to first class flights, or even charter private flights when desired instead of owning a plane.