"Trickle down" is an economic slur, it's not something economists believe. It's just what some people call a certain policy set.
As oppose to 'demand side' i.e. give tax cuts or money to the poor - they spend it, the economy grows.
Would you rather live in a world where there’s only 1 large firm because over regulation has created a high barrier to entry and little incentive to risk starting a competitor, or a world with many firms where it’s easy for people to compete and they’re incentivised to do so?