It happens when either major party is in control, but you're right: the Democrats lean toward more active regulation to shape outcomes in ways that often don't

It happens when either major party is in control, but you're right: the Democrats lean toward more active regulation to shape outcomes in ways that often don't benefit dominant players, while the GOP aims to erase regulation, often bluntly, and leave outcomes to the markets. As a practical matter, "markets" means "dominant players in the market". The GOP view on regulatory agencies is that they should look more like chambers of commerce, and as such, they end up stocked with representatives of those dominant players.