They enacted tremendous social change for their time, but they weren't dictators. Even if they wanted to abolish slavery or enable women to vote, it would have never happened because those were very unpopular views at the time. Only a (benevolent?) dictatorial regime can act against the popular will of the people to enact changes faster than the people can accept them.

Societal change has a hull speed, and attempting to exceed that hull speed will result in massive push-back and ultimately failure even if the change in question is viewed as 'obvious' in historical hindsight.

We can see the exact same thing happening today with the legalization of gay marriage or drugs. Both will be viewed as obvious a generation from now, but today they face tremendous pushback. That's not the fault of governance, that's just governance imposing changes that approach the societal hull speed on those issues.