It's a genuine mistake (/s), they thought that pro-business/anti-regulations would help their small business.
As with everything, they lied. It's about billionaires making more billions, at the expense of EVERYONE else - workers, but also other businesses. I'm convinced that all the rest, including the racism, xenophobia, transphobia, misogyny and overall bigotry are just tools to convince people to act against their own interests.
The republicans came within a vote of defunding Obamacare in 2018 and have talked about kicking out immigrants for a generation. To say that neither of those things were on the ballot is incredibly naive.