It's been a gradual process over the last two decades.
The cynical view would be that during that time they left the government twice to protest the government approving new nuclear power projects, and paid a heavy political price for that. They can't afford to do it a third time, and given Finland's position (can't rely on solar or wind during winter, can't build more hydro, can't depend on imports during the production troughs) it is highly likely that more nuclear will be approved at some point.
The non-cynical view is that the world has actually changed over that time. Reducing CO2 emissions is more urgent than ever, and there's no longer time to hope that we can instead reduce energy usage which used to be their preferred solution.
We’ve been promised apocalypse by now several decades ago, and literally nothing changed.
CO2 is just a misdirection away from actually dangerous things such is persistent chemical pollutants we dump into the ocean by millions of tons that cause widespread hormonal disruption or outright toxicity.
that is happening today, not at some unspecified point in the future. So weird nobody seems to be concerned about that.
