Maybe some gambling sites has formed a partnership with investment which promotes within the site same with the investment site that maybe promotes also the said gambling site. This is also to encourage more people to gamble or to invest on the same time. A marketing strategy indeed.
Investing on gambling site is quite profitable you can invest your money in bankroll of some of the gambling wesites where you can make profits in percentage of the total earnings from the site.
For example you can invest on
Bustadice gambing site here.