It can't, you would need major market makers to do that.
Instead, I think their model is genius. You split the losers bet loss. Smart, decentralized.
Discussion
In what way would you consider it decentralized?
To be fair, I have not looked through the code.
But the premise of signing on to a bet side a or b and then the winner(a) of the Oracle split the winnings in theory is incredibly easier to decentralized than having a market maker that pays out the fees based on odds.