Because society simply has mixed standards and very little empathy for men.
Our culture has (thankfully) shifted very far from the idea of the male role as sole protector and provider for the family. While that's great for women's independence, society hasn't changed the expectation that men should still primarily fill that role.
Young men are still expected to grow up to be financially successful, physically fit, willing to sacrifice their lives and happiness for their future families all while being completely emotionally invulnerable about all of it. Society is clear (and correct) that women can do any or all of that if they so choose, but it's totally also fine if they want to be a "traditional" woman.
We're at this halfway point where (compared to our traditional/conservative past) young women can choose any path they desire and it's acceptable and celebrated (which is a great thing). We just need to have that same expectation for young men, and make it clear.
When young men have problems, they very often are told to man-up or change themselves in some way (get a job, go to the gym, buy an expensive car)in order to fix it, when they need to be told it's okay to be upset, it's okay to share your feelings, it's okay to be vulnerable.
We can't send mixed signals that women are primarily attracted to rich, ripped, emotionally invulnerable soldiers. We've got to stop only celebrating men who are billionaires or professional athletes. Boys need to see their nerdy English teachers or average looking artists as role models.
I don't know how we can get there, but until we do our young men are going to continue this regression into toxic masculinity and far right ideologies.
This ended up way longer than intended, lol.