Why many Men are generally weak to Women ? ( Sexually Speaking )

If think there is multiple reason that explain this difference between men and women.
Biologically, men are mean to perpetuates their genes with many partners : reproduction is easy for them, it just cost the effort of reproducing and some material for producing semen
For women, the reproduction cost a lot : reproduction mean having a baby in the belly, it causes 9 month of vulnerability and suffering

The biological strategy of reproduction for men is the multiplication, the biological strategy for women is the selection of the best partner

this biological basis have influenced many societal construction in my point of views.
It’s a rational answer, based on biological strategy of a species : the reproduction

but other reasons (societal reasons) can explain it too

 

Because if we let nature and instinct rule our life the society will be very unstable : Brad Pitt and Orlando Blum will get hundred of ladies and people like me won’t have no one (remember that women are more selective and men are multiplicative)
For example : in a group of 5 men and 5 women, every men would like to reproduce with much of women, but women would reproduce with only one of them, the one who get the best reproductive attributes
So 4 men will be exclude of the game of reproduction

The western (and christian) mariage is both a win-win and a loose loose for men and women :
As a man, the mariage let me have a wife, because she can’t get Brad Pitt because he has to respect his mariage. But it prevents me from reproducing with other
For women, they get one male that can protect them during pregnancy and who can give their gene to the baby, (the mariage secure the fact that the man will take care of the family) but they won’t get George Clooney.

the western mariage is the best deal for a society to not fuck up

 

A strong man knows when to go for what he wants, but also when to be happy with what he has.

Some weaklings may fall for the next hot crumpet and end up throwing everything they had away, and even if that happens to be an elite businessman or world leader, then it only proves they are far from alpha despite what many people think of them. Indeed most high-ranking businessmen often sacrifice relationships with friends, family, even wives and children all to get whatever their instincts tell them to go for (whether that’s money, gold-digging sex partners or whatever), which is the opposite of alpha - a true alpha aims to succeed in every aspect of his life, not just his career.

Some people may believe men are supposed to sleep around, but not me. I have an innate sense of loyalty to any girl I develop attachment for, and this is the way to avoid the Coolidge effect. When you find a girl who loves you, and cares for you, just as you love and care for her, you remain loyal to her and picture her whenever you see the next half-naked piece of hot shit walk past you. That way, you’ll never end up losing what you’ve already got.

 

The practice of polygamy in islam is misunderstood especially by western eyes, i live in a islamic nation though i am no longer into religion -won't go out of my way to advertise it thought- even financially stable person only have one partner only the very rich(and few of them at that) or some isolated couples here and there due to fanaticism or what have you practice this(for the non-affluent since the man does not have a lot of power(money) they house is literally in a constant state of cold war).Your example with the sultan of Morocco is misleading, most medieval despot had multiples wives from the sultan, king, emperor, shogun or khan(pre-conversion); the christian monarch contended themselves to having official mistress(it is an actual title) they can get away with to do it since the money they are stealing from the people allow them to do it;
Your comment about being west african surprises me, although most polygamous marriage today are indeed located there saying it is "very common" is the just blatant miss-information they do not even make 1% of the population.
As for the actual reason why humans in general do not practice it Why sex is fun by Jared Diamond is a good introduction on the topic : https://www.goodreads.com/book/show/1991.Why_Is_Sex_Fun_The_Evolution_of_Human_Sexuality.

 

I think it's fair. Men are generally stronger, smarter and braver than women so if we weren't weak for them, they'd pretty much have nothing on us. I'm not a misogynist - there are definitely some women out there stronger, smarter and/or braver than some men, but I'm only talking about the general population of both genders. On the flipside, there's definitely some men out there who women are weak for.

 

Contentious. I've come across lots of brave women in the world. The Handmaid's Tale, although fiction, illustrates how strong women can be. Smarter? Who starts wars?" Stronger? Fair one, but that's not using the brain, and it often leads to trouble.