Most billionaires and large corporations have connections in, and make donations to, both major parties. The people who are critical of billionaires and corporations tend to also be the people that point out that the dominant faction of the Democratic Party (less sophisticated members of the critical group will shorten this to just the Democratic Party, without making the factional distinction) has for decades been, in economic policy terms, a center-right pro-corporate neoliberal group, not a progressive one.
2. Most don't publicly support GOP because they don't want to get cancelled.
PREFERENCE FALSIFICATION: Preference falsification is the act of misrepresenting one’s wants under perceived social pressures.