Why are you singling out wind turbines? The majority of the lost power generation capacity was thermal power plants (gas, coal and nuclear). One reason for the lost production for both the windmills and thermal power plants was because they weren't winterized. Why weren't they winterized is the question. Another reason for the lost production was a shortage of gas again because the gas system wasn't winterized.
This is a classic example of what happens when you have a lack of regulations to force for profit utilities to spend money to avoid disasters and then just when you thought it couldn't get worse these same utilities use the excuse that demand exceeds supply to jack up prices on those who didn't lose power.