You sold them to sort of a hedge fund, the bankroll consists of BTC, eth and ltc so as value of all of those increase, so does the value of the bankroll and therefore the value of BKB tokens.
Since BTC is 75% of the bankroll, he's pretty much still invested in BTC.
This is not correct, and part of the confusion. Here is the ICO information:
https://betking.io/ico/It appears the ICO proceeds were counted in USD and that determined the starting value in USD of the BKB tokens ($0.09286). The value increase in the BKB token has exclusively been from casino profits (
https://betking.io/bet/stats) - but BKB has not increased in value from the USD increase in the original bankroll. If it had, BKB would be worth far more - the initial amount alone would be worth $0.13+ plus the profits from the casino.