I'm curious how Grant's presidency is considered underrated. I admire him for taking unpopular stances around voting rights and civil rights (and particularly, he genuinely seemed to care about Native Americans in some real capacity) but his presidency was completely mired by corruption around him, so much so that there's entire wikipedia page devoted to it[0].
While I'm not going to claim nearly any president was without scandal (really almost none, sans maybe - maybe - George Washington), evidence suggests he was a really ineffective president all things considered, particularly in controlling his cabinet members and managing economic affairs
I think it's underrated since people generally rate it so poorly to begin with. His time in office is considered to be almost a waste since there was so much corruption by those who gained his trust and got into positions of power. Really, Sect of State Hamilton Fish was just about Grant's only good judge of character when building his administration.
Even though surrounded by corruption, he achieved important success by using his platform as by far America's most famous living person to push the country forward significantly on unpopular civil rights issues. To this end he developed as a public speaker and self-publicist while in office (as a poor judge of character he couldn't really rely on those around him).
While I'm not going to claim nearly any president was without scandal (really almost none, sans maybe - maybe - George Washington), evidence suggests he was a really ineffective president all things considered, particularly in controlling his cabinet members and managing economic affairs
[0]: https://en.wikipedia.org/wiki/Grant_administration_scandals