This question formulated by the poster begins with why. The poster presents what he believes is an answer. The question is formulated so: Rudolf Steiner described Asuras and Ahriman INSTEAD of (describing) flying saucers and aliens, the alleged answer is because Steiner wanted to be taken seriously, etc.
The poster also includes a digression on how he believes what Steiner wrote or said about supersensible beings Asuras and Ahriman
fits to
what the poster has ascertained not described in his information of Steiner - flying saucers, aliens.
The source of the poster's so-called answer and interpretation of Steiner's supersensible research seems to be the poster himself, in the way he understands himself, or as medium for what he names This Awareness. The poster does not ask why Rudolf Steiner rejected mediumism.