They also had to invent a new form of grease to lubricate the things because existing compounds failed quickly under the enormous bearing loads.
https://www.thenewamerican.com/tech/energy/item/15069-14-000-idle-wind-turbines-a-testament-to-failed-energy-policies
http://www.rbbengineering.com/wind-turbine-srb-main-bearing-failures/