Coexistence

Without elaborating, I still think JS’s view seems to overemphasize or even make the bhairavasrotas/kaula dominance exclusive. That said, when we take the evidence from throughout the country I think at the great kShetra-s the different branches of the shaiva-shAsana simultaneously existed. We see this at the great siddhAnta-dominated temple centers in the drAviDa country; we see it Nepal and Kashmir.

Moreover, rAmakaNTha-II’s mata~NgapArameshvara commentary suggests that siddhAnta tantra-s were being accepted and interpreted as per their internal tradition by even by non-saiddhAntika-s. I take this to imply a general socially dominant saiddhantika substrate among whom various shaiva schools still persisted and in some cases ascended.

I’m willing to accept Schwarz’s findings of evidence for various bhairavIya traditions – have found some myself, but would not see that as exclusive or even dominant for much of the pre-Islamic age in central-peninsular India.

Anyhow a coherent treatment of all this would need time and medium different from this and might not convince someone with a contrary view.