As a note: The technologies used as topload can for practical purposes also be used as baseload, and if overbuilt, technologies normally placed in the baseload bin or the intermittent bin can be used to load balance if you set up the system to spill power. And a large enough intermittent grid would go towards a pretty stable average. But let's stick with the conventional terms for now.

Even though the grid is built for baseload plus topload the market, at least in EU, is built around getting paid (and paying) per kWh, with the price set by demand and supply at each moment. And in such a market baseload has no advantage on intermittent, they both simply get the average price over time, so the difference is on the cost side where wind now has the advantage.

The external costs of adapting the grid is laid at the feet of the entity responsible for the grid, but then again they tend to have monopolies, so they manage.

At least in Sweden, we have had this market system since the early 90ies, so my guess is neoliberalism + EU. Other markets are possible, we had a very different energy market before the 90ies, but I don't think a fundamental reform is likely.