You can live in Singapore, visit Monaco for a weekend, then quickly fly back. You can have a team of lawyers and servants on hand. Planning and advising what citizenships to gain and which ones to lose. I think this was just one advice he received and he let them set it up for him.
With that much wealth, taxes all of the sudden are handled differently. The money you can pay a team of tax lawyers and accountants to offshore it, and protect it, is a drop in the bucket, compared to the tax you'd pay. You'd be a fool not to do it.
But year, at first, as someone who also jumped through years of red tape to gain citizenship, this is baffling, but you have to realize these individuals live in a different world, by different rules.
At 15% long-term capital gains tax rate on $3.84B (4% of Facebook),
He saved $576 Million by giving up his citizenship and moving to Singapore.
He may have sold some stock to private investors but I don't think that's what you meant.
I'm currently in H-1B status and work for a top tier hedge fund. I recently resigned because I decided it was time to go full on with my own company, and even though I have lived here for 2 years, paid my share of taxes, and have enough saved up to support myself for at least 1.5 to 2 years, if I don't succeed/raise money to sponsor my own H1B in the next few months (or take a new job) there's a chance I will have to go home.
Oh, and even getting a chance at getting those few months, is dependent on the USCIS approving my change in status from a specialist worker to a "tourist."
There's just so little room for error as an immigrant, but the fact that you can make lots of mistakes is one of the things that makes the US so awesome for gutsy Americans.
Immigration is a messed up thing and it's just sad to see someone throw a citizenship away that so many people would fight like crazy for. I doubt he would have gotten that first chance to make it big anywhere else.