"Rational" does not mean "smart", "good", or "beneficial to the society".
It was the choice businesses made, because they believed it was the best way to make profit in the energy market. The EU agreed on emission quotas and set up the emission trade system, in order to let the market choose how to reduce emissions. The market chose natural gas, and the politicians allowed that, because they believed in the wisdom of the market.
I don't believe that for a minute - since now the market is choosing nuclear the moment the EU allowed it to be considered green. We were waiting for it for a decade with projects in hand and now there are entire new reactors being built, all so suddenly. Experts from my country were lobbying for that at least since 2008. The EU commission has chosen feels instead of evidence and nobody will ever pay for that - except Ukrainians with their lives and poorer Europeans with their savings.
And BTW this isn't just about the market - our state wanted to support nuclear but the EU sued it for unfair competition. Oh no, the German electricity producers might make less profit from their Russian gas, what would we do?!?!?
It was the choice businesses made, because they believed it was the best way to make profit in the energy market. The EU agreed on emission quotas and set up the emission trade system, in order to let the market choose how to reduce emissions. The market chose natural gas, and the politicians allowed that, because they believed in the wisdom of the market.