As to why the entire structure exists in the way it does, this being the first foundation of the Sefirot, one may not ask for a reason, because this depends on the Supreme Will. However, it is permissible to investigate and seek to understand everything that comes after this foundation, namely how these levels function in the government of the worlds.
Having explained this first foundation, we will now discuss where it is forbidden to investigate and where it is permitted.
As to why the entire structure exists in the way it does, this being the first foundation of the Sefirot, one may not ask for a reason... As I said above, this first foundation is Keter, of which the sages said, “Do not search out that which is too wondrous for you” (Chagigah 13a). For the light of Keter is the law that is the first of all the levels. This law ordains precise levels and their arrangement in just the way they are now. Thus Keter is literally the totality of everything, and Keter is bound up with Eyn Sof, blessed be He, Who is the all-powerful Will.