~45% of people work for companies of less than 500 people, ~12% for the govrnment (federal, state, local), ~6% are self employed. That leaves less than a half for all the companies >500, and only a tiny minority of them have an outsized influence on politics.
EDIT: Also, if there were no big corporations, people would still work and pay taxes. No sane statesman would purposefully build their countries economy on non-state-controlled megacorps.
