Both parties represent the capitalist class, not the masses. I wouldn’t go so far as to say it is all just theater to trick people or something, but their interests as political parties are much more closely aligned with each other’s than they are with the working class. That’s why the Democrats will happily pass bills unpopular with anyone but the rich, or why they will claim to oppose the Republicans, but when they get into power they don’t undo any of their disastrous policies, sometimes even expanding on them.