They build what's most profitable.
Nukes are the lowest cost to operate but the build costs coupled with the end of life shutdown expenses takes all the profit out of owning one.
If Nuke plant owners were on the hook for disposal of their spent fuel rods the first one would have never been built.
Of course the tax payers pick up those costs.
Combined Cycle and renewables are profitable so that's what they build, pretty simple.
