This BBC article lists Nicholas II of Russia (1868 - 1918) as the 7th richest person in human history, with an estimated wealth of $300 billion (measured in current USD).

How did he accumulate such a fortune? Was it a result of generations of land ownership and kleptocracy?

Finally, what happened to the fortune after his execution? Was it seized by the state? Moved overseas? Stolen by others?

Thank you for any insight.