…it is specifically the holiest souls that evil attempts to grasp

After [these two incarnations,] they had to be purified. For as I have already told you (Likutei Torah in the writings of the Arizal on Ezekiel), they were holy and powerful souls, but evil's grasp of them spoiled them. Once they would be purified and be rid of the sickness of impurity, they would be manifest as holy souls. As you also know, it is specifically the holiest souls that evil attempts to grasp.

We can perhaps understand this as follows. Rabbi Shalom Dovber of Lubavitch states that someone who has never committed the sin of "blemishing the covenant [of circumcision]" on some level cannot truly relate to the inner dimension of the Torah. Now, the most basic meaning of "blemishing the covenant" is wasteful emission of seed, but it can refer also to any sexual aberration, and more subtly, to any lapse of divine consciousness resulting from being seduced by some foreign promise of spiritual fulfillment. After all, wasteful emission of seed and sexual aberration in general is a misdirection of a person's potential into the wrong channels, and focusing on anything other than G‑d is essentially the same thing. The only difference is that in the first case we are talking about reproductive and/or romantic energy while in the second case we are talking about mental or creative energy; in either case, the potential that should have been used to propagate and promulgate divine consciousness throughout reality has been squandered.

But what causes a person to do this? If, as the Kabbala insists, we are all "hard-wired" to fulfill our purpose on earth, to make reality into G‑d's home by propagating divine consciousness throughout it, why would anyone do anything contrary to that end? The answer is that evil temporarily succeeds in convincing the person that the sin it is enticing him to commit will in fact serve this purpose, that the "high" he will get from committing the sin (or from diverting his attention from G‑d momentarily) will enhance his life, re-energize him, re-inspire him, or in some other way accomplish something in short order that it would take a long time to accomplish through the normal channels. Evil seduces us with a shortcut, because it knows that we know that the path to true, holy self-refinement is a long, hard, and tedious one. Evil plays on and capitalizes on our divine imperative and our impatience and frustration over how long it takes us to make real progress.

…anyone who has never fallen for this ruse...cannot really relate to the inner dimension of the Torah.

Hence, Rabbi Shalom Dovber said that anyone who has never fallen for this ruse in some way - even if only in a very abstract, refined way - cannot really relate to the inner dimension of the Torah. This is because the inner dimension of the Torah addresses not the do's and don'ts that the revealed dimension of the Torah addresses, but the more profound issues in life, such as "what is the meaning of life" and "why is there suffering in the world," etc. If a person has never been bothered and frustrated by these questions enough to fall for the bait of a shortcut to their solution, the inner dimension of the Torah will not speak to him.

Now, all souls come [into reality] with states of chesed and gevura, which are derived from daat. Coupling is a function of daat, this being the mystical meaning of the phrase, "And Adam knew his wife Eve." (Gen. 4:1) Coupling is referred to as "knowledge" because the seminal drop originates in daat [literally translated as "knowledge"].

[This is] also [true of] Moses' generation, as is known, for Moses personified daat and thus his generation was a generation of daat, as we have explained elsewhere. (Etz Chaim 32:2) However, they were drawn to evil.

This is evident from the fact that they suffered the oppression of the Egyptian exile and slavery. Some deficiency of theirs caused a blockage in the flow of divine beneficence to them.