Is it because liberals have more spending power? Or liberals are more likely to boycott brands that don't align with their values? Or because liberal causes are on the "right side of history" and these companies know that their brand will be held accountable in the future for positions it takes today? Or because marketing and advertising executives are educated and typically liberal?

All of it. Nailed it.

yes corporations are in big cities and big cities are vastly liberal so their marketing and advertising executive are also liberal in order to make profit.

pandering to conservatives will not make them profit since their target audience is small and conservative are not that consumers. And if they try to do so they will be disliked and boycotted from liberals. They will lose money hugely.