[2.1.6] Not sure if bug - heresy doesn't overtake main religion

[IntoTheMaelstrom]

As in title. Maybe I need Rajas of India DLC to have it happening, but since I bought the game (I think) it never happened to any religion that it overtakes main branch (like often happens with zoroastrians). Just look at poor zikri

 

[Servancour]

If I remember correctly, heresies can become the main branch and replace the old orthodoxy if you have the Sons of Abraham DLC. Do you have that?

 

[IntoTheMaelstrom]

Facepalm, because I don't. Thanks!