Assuming your Monopoly house rules allow arbitrary contracts (if they don't, they should) the non-winning players can extend credit to each other, and allocate their combined resources very efficiently to try to beat the winner.
It's very hard as a single player to beat a credit union. So the winning player will want to build some sort of alliance with at least some of the losers to make their coalition weaker, which will pull those players up the ladder and give them a chance, and so on. It creates a mostly good dynamic of cooperation for self-preservation.
In the end, one person wins, but it's often a close race.
(This works best if you play with the same crowd every time, because then people have reason to build trust with each other and won't suddenly default on a huge loan without feeling the consequences of it.)
