MICE is the acronym for categorizing the common motivations for espionage:

M - Money/Greed

I - Ideology/Divided Loyalty

C - Coercion/Compromise

E - Ego

Sometimes, I think we look at people who are this wealthy and think they should be immune to these kinds of shenanigans, but I'd wager that the -ICE becomes even easier to exploit in people once they no longer need money, if they were already susceptible to it to begin with.