I honestly don’t understand how renewable energy generation has become a party position.

Serving entrenched interests. Preserving their profits in the short term and giving them more time to limit their losses from transition to renewables.

Advocating for nuclear is the same, probably just another tactic to delay on renewables. To the degree that it goes anywhere, though, it'll be funneling tonnes of government money to large entrenched interests (feasibility studies, industry framework design, reactor facility design, or the unlikely event of actual construction).