I know it always supports big business. And it’s a reactionary force that people in power turn to when things go badly for the workers and they think of revolt.
But fascism also demands genocide and killing of millions of people and that would only hurt the capitalists, no? Because these are people who would otherwise be working and increasing profit used to increase productivity etc etc etc. But if you kill them you reduce the labor force and thus drive up the price of labor, reducing your profits, and thus what you can spend on improving productivity? And other countries which didn’t do so would become more advanced, leaving you behind.
You can think of "exploitation" and "profits" as two complimentary dials. If profits go down by 50%, but exploitation goes up by 55%, then capitalists will consider that good for themselves in the long run, since it entrenches their power in the system. Once climate change starts to really accelerate, profits might go down in the short term, but if fascism keeps any kind of left-wing revolution from happening, capitalism will only get stronger in the long run, since people will be more desperate for work/wages.