It's not so simple. They're cheaper than building non renewable, but are they cheaper than keeping the current plants running? Also, energy consumption keeps growing, and in many places, new generating plants using renewables usually only take care of the growth, and doesn't allow for room to take older plants out of operations. If we don't make huge efforts to reduce our energy consumption, I doubt we're going to get rid of non renewables so soon...

Currently they are cheaper despite the financial support for fossils but back then it was not and not enough was spent on research