The profit margin may be lower, but I don't see how fossil fuels could continue to maintain that margin as renewables undercut them. What utility would run a more expensive generator than a less expensive one, all else equal? Expected profit is higher from a wind farm that can continue to run for decades than a coal plant you have to shutter a partway through its lifespan because new, cheaper energy is available and grid stability functions are taken over by batteries instead of spinning turbines.