Muslim women are only allowed to expose their face and hands according to the traditional understanding, and even the face is a lot according to some who order women to cover the cover the face as well. Many sheikhs become angry if a few strand of hair get exposed.
But Christian women don’t have such strict, rigid dress code for them, as you can see in the right picture, dress like this where they don’t cover their arms, legs, head, neck would be accepted as modest by their Churches. People on this subreddit won’t find any immodesty in them either, but a lot of Mainstream Muslims surely do.
What is the reason?
As someone already stated above feminism and the work of thousands of women over the centuries has done most of the work. But I think it’s diversity as well, insular cult mentality does not survive long when exposed to freedom. And the christians are always running around proselytizing, exposing themselves to pagan ways.
It’s also that they just don’t read or follow the Bible really most of western christianity is just “good vibes”
Here is 1 Corinthians 3-6
“But I want you to realize that the head of every man is Christ, and the head of the woman is man,[a] and the head of Christ is God. 4 Every man who prays or prophesies with his head covered dishonors his head. 5 But every woman who prays or prophesies with her head uncovered dishonors her head—it is the same as having her head shaved. 6 For if a woman does not cover her head, she might as well have her hair cut off; but if it is a disgrace for a woman to have her hair cut off or her head shaved, then she should cover her head.”