But more research into renewables (new solar cells, turbine designs, geothermal drilling techniques and such) makes them even more cost competitive, which puts immense pressure on fossil fuels. That highly experimental stuff competes with fusion for funding, and is something manufacturers aren’t necessarily able to pursue.
Renewables are of course cheaper in some cases, but if renewables were drastically cheaper with breakthroughs, I think lobbying would only get fossil fuel companies so far.