@NeoSmile
My idea was similar to your just hadn't fleshed it out well. The hope i was speaking in religion is like a carrot after the stick. You want to go to heaven follow the following steps depending on your religion
a. give donations to churc to wash your sins off(indulgence, sparked the protestant movement)
b. inflict self-harm
c. pray everyday and never doubt your belief( in past, now many religion tell believers to doubt so their faith is stronger)
d. Fight wars: crusade, jhihad etc.
A few off the top of my head, not exhaustive by any means. As stated prior it was like dangling hope while putting the fear of hell if they didn't follow.
As for the power of pope, even in medieval times it wasn't exactly true they had absolute authorit. The pope did hold considerable influence but by no means was it absolute or they would be no anti-pope and so many branches of the christian faith.
The pope also needed money(try searching indulgence-gate) and support of their family(most were sons of prominent families), and so it was more of a give and take relation. The pope could depose an emperor and sometimes even a king could depose a pope
The drugs part although right wasn't wide-spread in the true sense of it. Like cocaine was actually used as a dental anesthetic even in late 1800's, so what was banned then and now is different. And wide-spread use can lead to the downfall of empires as seen in the opium trade between europeans and China, where the chinese were becoming slaves to the drug. As such even tough it existed to an extent it was more hidden than the open way this is shown. Even then the general devotees and priests weren't addicts. It was the select circle(basically a cult) who endorsed such behavior.
This is from my limited knowledge of reading up on some histories as I had gotten curious, so in no way am I saying you're wrong but just trying to put across my views. Apologies in advance if there is any mistake in my points.