It wasn't nothing to do with them, but it was mostly not to do with their intrinsic characteristics, and a lot to do with how they were managed on the grid, and how some of them were not actually acting as they should (which was also true of some non-renewable sources). Saying 'nothing to do with renewable energy sources' when the report spends half its time talking about renewable energy plants and how they contributed to the problem is really not helpful (as unhelpful, IMO, as going on about how it proved renewables intrinsically make a grind unstable, because it gives credence to that argument).