> Fossil plants however can be fully decommissioned with 0 remaining costs

You say that, but someone still has to pay those costs which are rarely factored in and are significant.

To the north of my state we are faced with the costs of decommissioning and removal of 35 platforms, 6076 km of pipelines and static umbilicals; 483 subsea lifts; 11 floating facilities, 120 risers and 548 wells to be plugged - in addition to kilotons of offshore steel and concrete.

eg: One project is the Northern Endeavour is a 274-metre floating production storage and offloading (FPSO) facility. The Australian Government took responsibility for the decommissioning of the Northern Endeavour after the liquidation of its owner.

These are non trivial undertakings with costs running into the billions.