@bondar One concept that may help you think through this, though you may already be familiar, is progressive revelation. The best example is Christ in the Old Testament. Another example would be the Trinitarian nature of God. God did not hand Moses a list of theological beliefs to hold, but rather revealed Himself throughout salvation history.
So no, the Old Testament does not contain as many details on ‘the accuser’ as the New Testament. But that does not mean that the idea of a personal adversary - Satan - was invented. It fits the pattern we see of progressive revelation.
Regarding the specific theory you mention about existential frustration - that is only one theory. I could make up a dozen other sociological explanations if I wanted to, but that does not make them true. At the end of the day, I think we can root ourselves in progressive revelation and look to Christ, whom we trust, as our authority on matters where we are unsure. Jesus clearly believed in a personal adversary.
Luke 10:18-19 - 18 He replied, “I saw Satan fall like lightning from heaven. 19 I have given you authority to trample on snakes and scorpions and to overcome all the power of the enemy; nothing will harm you.
First, Limbaugh notes the importance of progressive revelation for understanding how Christ is revealed in the Old Testament. “Progressive revelation” simply means the original audience (and even author) didn’t share the same perspective as New Testament readers. While the Old Testament does contain legitimate testimonies to the person and work of Christ, many of these passages can only be understood as pointing to Christ retrospectively. Though always present, an Old Testament text’s Christological significance only becomes clear in light of subsequent revelation. Progressive revelation is vital, then, since it allows us to affirm the Old Testament’s Christological significance without straining the text beyond what it can exegetically sustain. Limbaugh generally allows for Christ-centered passages to emerge with the help of later revelation. Thus he remains true to the concept of progressive revelation, which he describes early within The Emmaus Code . For a popular level book, this is a commendable feat.