Basically to enable recouping investments in primarily wind/solar since they have no real ongoing input costs. The article explains it well, but doesn't paint a good picture until those future storage technologies are here.
Renewables bid low, because that accurately reflects their costs, which the bidding system is design to reveal, like an auction.
The only problem is that gas is scarce and really expensive. And people seem allergic to any solution which isn't to subsidize the cost of gas, driving up demand.
It's designed to repay investment into non fossil fuel power supply that don't have those variable input costs.
The wider range of prices is the new thing, but the cheaper sources getting paid at the marginal price was always the intention. It stops people inflating their bid, which renewables could do if they wanted to queue jump, they'd just be risking that they are the most expensive renewable and they don't get picked, and get paid zero.
It incentives the lowest cost producers (as long as it's regulated properly, see the Australian experience with gas cartels abusing the system).