Importance of vidvAn-s
As I have earlier clarified to @goghritaM there might be sAdhaka-s who primarily develop as yogin-s on the siddha track with acquisition of mantra-siddhi-s and those who primarily develop as vidvAn-s with little mantra-siddhi-s. As abhinavagupta laid out the latter is more important for the system as they preserve tradition. Hence, even though the first might look immensely charismatic to the lay devotee it is important that the system focus on development of the latter, and ensure that the siddha-s don’t stray out of the bounds of the system.
Importance of siddha-s
But more generally I think (and those with a “modern” bent wont like it) that at the heart of mantravAda lies the attainment of siddhi-s.+++(4)+++ However, most people don’t attain siddhi-s. But for a tantra revelation to become manifest it needs a siddha who can show the limiting possibilities. Hence, there would always have to be some who are both paNDita & siddha who record the prayoga-s upon siddhi. Else it will be a false scripture.
Thus, even from the itihAsa-s we hear of vidyAdhara-s & siddha-s – there was always a cloud of pure siddha-s but a small subset of them were also paNDita-s who could then “reveal” the revelation as part of the mAnavaugha & teach it by founding a lodge. I believe from thence the concept of the yuganAtha-s and their role in obtaining or reobtain scripture was recorded in tradition.
mAnavaugha, siddhaugha, divyaugha
To be clear: the mAnavaugha sprouts off the siddhaugha. A mantravAdin learns his mantra from his teacher, his teacher from his so on. This parampara is the mAnavaugha. It ultimately culminates in a siddha.
Now it is believed there is a higher transmission where a siddha produces other siddha-s either as children or through dIkSha. Thus mIna is said to be the son of matsya, whereas gorakSha was a disciple. This transmission among siddha-s is technically the siddhaugha. But where does the root siddha ultimately get his/her transmission. That’s from the divyaugha. Now it does seem to me that some siddha-s do emerge spontaneously among the mAnavaugha – like any of you gentlemen have a non-0 probability of becoming a siddha – may be minor one but still. Do all these siddha-s spawn siddhaugha-s? Probably not. But the historical telescoping in tradition leads to some of these siddha-s being placed in a “notional” siddhaugha, much like the lists in the extant nAtha traditions.
matsyendra
I think matsyendra was unique: as the yuganAtha he was both paNDita &siddha at the same time. Not a paNDita in the sense of 1 who writes in masterly Skt but 1 who boldly writes his insights as a systematic text as the sole author rather than contributing to an Agamika compendium. In this regard he is rather unique; there were some other like that on both on our side that of the bAhya-s. However, the majority of his apabhraMsha-using successors, irrespective of the force of their charyAgIti-s were mostly in the siddha mold. Though among the later rasasiddha-s evidently there were some paNDita-s.