Women on average have a worse understanding of things which a competent political leaders must have a good understanding of. Also, you typically want only the best of the best to be political leaders, and probably similar to the IQ curve, relative to men there are less women on the high end of the spectrum of traits which make a good political leader, even taking into account their already lower average competence.
And yes, exceptions exist, but not beyond a certain point. Let’s use an example in lifting because there’s a clear way to measure it and there’s numbers involved, which makes it easy to get a point across. The highest male squat in the same weight category is higher than the highest female squat. The male might be 500kg, the female 350kg, these aren’t exact numbers but you get the point. There are still many men who lift between 350 and 500. But there are no women who lift more than 350. No more exceptions beyond that point. Politics works in a similar manner. Therefore there is no benefit to allowing women in politics if your goal is to have a functional, optimized political system ruled by the best of the best, in the same way that if your goal is to lift something heavy, you look for the best man for the job, not a woman, and even if you find a woman who can do the job, a man could have done it more efficiently.
And that’s only one reason.
There are plenty more.
For one, that politics is an alternative to war and it only makes sense to do politics in the first place if war isn’t more profitable, and since women don’t affect the outcome of war, unless you want war it makes no sense to let them influence politics, because that just makes war more profitable for men.
Another is that women have another important job that men can’t do, which is to give birth to babies, and women who become political leaders have extremely low fertility rates for obvious reasons - politics takes a large chunk of your time, especially if you’re in top positions, like Merkel.
Whatever angle you’re looking from, it makes no sense if things like functionality and long-term survival of the society mean anything to you.