They’ve changed.

Moral norms are always shifting around a bit. That’s because they’re partly based on how any group can live and thrive together, and the material context changes.

If your society feels itself surrounded by violent enemies, then norms of bravery and heroism and standing up for yourself come to the fore. If your society feels more secure and peaceful, then norms of forgiveness and tolerance predominate.[1]

Moral norms are also a source of power. Control over what women are allowed to do. Or what sexual practices are acceptable etc. can often be leveraged into greater power. For example, if you can only have sex in marriage, and marriage has to be licensed by the church … well, that’s a pretty solid business model for the church to be in.

So norms also change in resonance with shifting power relationships.

Finally, there’s a mimetic component : that norms are copied, and sometimes a norm from a subculture can infect a wider community than the sub-culture within which it originally appeared. That can give rise to more arbitrary “chaotic” changes too.

[1] It’s actually not quite so simple, sometimes difficult circumstances require more subtle negotiation and softer approaches. And sometimes the comfortable can adopt heroic norms for reasons of vanity. But context is still asserting its influence.