Invention of new weapons/gases was HUGE, but Disease and famine was also a large factor
The Enlightenment was an era where people started realizing that they had (human) rights, realized that the monarchy + aristrocrats/ rich ppl in general shouldn't do whatever they wanted to do (like kill a bunch of ppl for saying smth against the Crown's beliefs), realized that they are capable of believing and doing something more than just living as a peasant.
The French had really sucky monarchs (like King Louis the Thirteenth), and frankly, they were sick of living in famine and poverty, so it was kinda like being in the right place and at the right time-- they overthrew their monarchy, now aware that they had these rights (inspired by the Enlightenment). "Liberté, Égalité, Fraternité" was the slogan. Liberty, Equality, Brotherhood = everything the monarchy wasn't.
The Radical Republicans believed blacks were entitled to the same political rights and opportunities as whites. They also believed that the Confederate leaders should be punished for their roles in the Civil War.
