Why have punishments for crime softened in the west in last two or three centuries?
I have a few theories:
One is it was harder to catch criminals back then, so when you did catch them, you had to make an example of them.
Two is people had more of a sense of community, of togetherness, so when you transgressed the law, people were more hurt by it, more offended.
Three is life was poorer, nastier and shorter, people were harder, tougher, it took more to deter them from committing crimes, and they had a stronger stomach for violence, they weren't as apprehensive about dishing it out.
The king and the aristocracy made the laws, and they were often above them, so they had nothing to lose by making tough laws and everything to gain.
It was their own order they were maintaining, why break their own self serving order, and why not strengthen as much as possible?
We have more resources now, to both quarantine and rehabilitate people, back then they didn't have the means to take care of criminals, certainly not very well, so conditions were poorer, and punishments swift: amputation, execution.
Not only do we have more material resources, but we have more psychological ones at our disposal additionally, we have more effective drugs now for treating the sorts of mental illnesses that're thought to exacerbate violent or criminal tendencies, and we have more in the way of counselling and therapy in our inventory.
It was believed laws were made by or at least given the okay by the Gods, so you weren't just breaking a village's law, a town's or even just a state's, but the divine, absolute and objective law.
Laws have always changed, but probably more now more than ever, as the pace of society as a whole is changing, continually updating and supposedly upgrading, reassessing and evaluating its morals and values, its ethos, and so the law is viewed as more arbitrary now, questionable, and so we're more hesitant about punishing people severely.
We're also more familiar with how things are done in other countries, and even in other provinces or states, which makes laws seem even less immutable.
Females are having more of a say in politics, and there may be a tendency for them to be more lenient when doling out punishments, at least when the crime doesn't affect them personally.
While sometimes it can seem like it's worse than ever before, violent crime has been decreasing significantly for centuries, and so it may seem less necessary to root or stamp it out powerfully and speedily whenever and wherever it's found.