The story here doesn't really seem to line up. Generally, for a fossil fuel based system, coal is cheap, but slow to start (nuclear is similar in that regard), so it is used to generate the base level of electricity needed. When demand starts to go up, generation is added by natural gas plants that can start and stop more easily. Whether natural gas is cheap or not, the fact that these plants aren't always on means that the energy they produce will cost more.
Solar/wind are predictable enough that they can be used to reduce the baseline demand, supplied by coal. Peak demands still end up getting addressed by natural gas.
If renewables were putting the expensive natural gas generation out of business, we'd see those plants closing while coal stays level, but we see coal going down and natural gas going up.
Using the Texas example from the article, you can see their coal plants closing or converting to gas while more gas plants open. https://en.m.wikipedia.org/wiki/List_of_power_stations_in_Texas