Your mistake is treating capitalism as a static "status quo." It isn't. Capitalism is a dynamic process of constant, disruptive revolution. It actively destroys the ecological status quo every single day. So if "conservative" means upholding the prevailing state of things, then defending the physical world against capitalist expansion is conservative. You have to radically change the economy just to conserve the environment.
The train analogy only proves my point. If a train is accelerating toward a cliff, letting it run preserves the engine's current operation, but it radically destroys the train. Hitting the brakes disrupts the engine's operation in order to conserve the train. I want to disrupt the capitalist engine to conserve the physical world. Communist means, conservative ends.