Leibniz - On the problem of compound Monadological structures

I would like to open a discussion concerning various topics which can be seen as problematic in the philosophy of Leibniz and others

What Leibniz makes clear to us ( in Monadology) is that it is not at all clear why do particluars form structures. In fact its higly problematic when he assumes elementary, unperishing points called Monads (centers of activity and thought - which is here the same thing) We can clearly see this is a problem for Leibniz, because he is obliged to say two things. 1. Monads do not have windows, so they can’t be affected by other Monads. 2. (As a consequence) we have to postulate pre-established harmony to explain their coordination. For Leibniz, there is no other way he can explain it. So he does not know why there even exists this organization in the first place, which breaks his system, because he postulates in the first sentence of his Monadology that there in fact are compound structures, from which (he claims) we see that there have to some elementary particles. I do not think there has been any progress on this question down to our time from the pre-socratics. Leibniz is bold enough to assume pluralism of substances having a value of it’s own. Pre-socratics dissolved particulars in something general. They had to explain particulars by Necessity, becuase it simply mattered very little- it did not become a problem for them. Leibnize’s first postulate in Monadology serves a summary to ancient physics. They asked HOW it happens that compound composed of something elementary and unchanging. It was a mechanical question. Now Platón and Aristotle wanted to know WHY it happens in the first place. For they adhered to Anaxagoras and his concept of Nous, which is Leibnize’s pre-established harmony. Till this day it is still a question HOW it happens. For physics found laws governing formations of structures. But WHY elementary particles should be tuned to each other, WHY they are even made to go further, and not simply stay what they are ,is still a mystery. It should be remembered that Leukippos was much further than modern science. Because he knew that given atoms and empty space, they will just stay that way forever. So he postulated Necessity, as every bad philosophy does. He didn’t know why, so he said it must be so. I think Democritus hit on that too, se they adhered to Necessity- it has to be like this. This is an aswer constsntly re-affirmed by quantum physics. It’s trying to pin down a mechanism which could explain HOW are particles constitueted to form structures. But the real question is WHY should there be something unchanging forming something changeable, and what prones this formation have not been even properly asked. I see it only in Leibniz, but he does not say it explicitly

I will happily enter into further discussion, feel free to attack whatever statement you feel uncomfortable with. This is not a argumentatively coherent thesis, I simply do not understand it and want to have a better grasp of it.