Because the way how the EU electricity market operates first to supply electric power are the power plants with the lowest operating costs. This are usually renewables and nuclear power plants. Both are capital expensive and cheap in operating costs.

Usually the capacity factor of European nuclear reactors is higher than 60%.

olkiluoto-3 nuclear reactor, had capacity factor 70% in the year 2024:
https://world-nuclear.org/nuclear-reactor-database/details/o...

Mochovce-3 had capacity factor 74% in the year 2024:
https://world-nuclear.org/nuclear-reactor-database/details/M...

In the U.S. they really try to get maximum from nuclear reactors.
https://world-nuclear.org/nuclear-reactor-database/details/W...

Europe would be better served by doing, what France did in 1974.

"As a direct result of the 1973 oil crisis, on 6 March 1974 Prime Minister Pierre Messmer announced what became known as the 'Messmer Plan', a hugely ambitious nuclear power program aimed at generating most of France's electricity from nuclear power. At the time of the oil crisis most of France's electricity came from foreign oil. "

"Work on the first three plants, at Tricastin, Gravelines, and Dampierre, started the same year and France installed 56 reactors over the next 15 years."

https://en.wikipedia.org/wiki/Nuclear_power_in_France#Messme...