The $200 billion figure was estimated by financier Bill Browder who, in a testimony to the U.S. Senate Judiciary Committee in 2017, said that Putin amassed most of his wealth after a Moscow court jailed oligarch Mikhail Khodorkovsky in 2003 for fraud and tax evasion:

“After Khodorkovsky’s conviction, the other oligarchs went to Putin and asked him what they needed to do to avoid sitting in the same cage as Khodorkovsky. From what followed, it appeared that Putin’s answer was, “50%” He wasn’t saying 50% for the Russian government or the presidential administration of Russia, but 50% for Vladimir Putin personally.”

Following the dead link to its archive, the latest snapshot has nothing about this “50% blackmail” thing. And if you think about it, this whole story makes literally no sense.

Also, this story is literally the only explanation given in your source of Putin owning $200 billion.