The best solution I’ve heard started by looking at who benefits from this norm [older women] and wondering whether they could have contributed to it. After all, the strength of this norm has been increased in the last sixty years or so, which coincides with the period in which women’s power has increased.
The primary mistake you're making here is confusing correlation and causation. Even if you assume that the feminism movement has been the sole cause of this, the status gains older women have made are orders of magnitude smaller than the status gains all women have made. (If you disagree with this, I'm going to tap out and let someone who is more well versed in the history of feminism make this argument.) This may have been a small bonus for them (I doubt it even entered anyone's consideration) but to me this seems like saying people invest their money because they don't want to store it in a chest in their closet. Sure, it's nice that they don't have to lock it up, but the primary reason they are investing is to make more money.
Why don’t men go for younger women? That’s not quite accurate, because they do, but we seem to have a cultural norm against girls who have recently exited puberty, even though they are highly fertile. Some time in the last few hundred years, we reached a cultural norm that as a man gets older, it’s increasingly less appropriate for him to be with a sixteen year old. That’s not long enough to override thousands of years of evolution, so what could have contributed to it?
The best solution I’ve heard started by looking at who benefits from this norm [older women] and wondering whether they could have contributed to it. After all, the strength of this norm has been increased in the last sixty years or so, which coincides with the period in which women’s power has increased.
One alternative I heard recently is that it doesn’t make sense biologically to go for women who are recently post-pubescent, as they don’t make the best mothers. Instead, a slightly older woman [mid-twenties] makes sense to be the best mother. This is perfectly plausible.
Another, less plausible, suggestion I’ve heard is that it’s to do with mental capacity. I find this unconvincing because we have few objections to a high-status man dating a beautiful but low-intellect woman.
Thoughts?