How A Philosophy Becomes A Religion

I understand that, in China, Taoist philosophy and Taoist religion are organized separately: different founders, different authoritative texts etc. Is Buddhism a religion or a philosophy? Both: philosophy, because its teaching is based on analysis of experience; religion, because it refers to the transcendent although it does not personify the latter.

Tatiana Thane explains her Cosmenosis to Chunderban Desai, calling it a philosophy rather than a religion but ending with an assertion that is mere religious hope.

Physical fact: an ancient space-faring race left relics on many planets.

Cosmenosist assertions:

reality perpetually grows and transcends itself;
the duty of the highest is to help raise the lower;
the Builders were too widespread to become extinct;
so they must have gone on to a higher level;
"'...on their chosen day they will return, for all our sakes.'"
-Poul Anderson, Captain Flandry: Defender Of The Terran Empire (New York, 2010), p. 130;
there are rumors of a forerunner.

The Ancients were the Chereionites. They will not return. The forerunner is a cruel deception by the last Chereionite - a deception on a scale unprecedented in human religions.