If you truly believe, do you attempt to convert others? Do you proselytize your truth?
If truth is self-evident, there is no need: Your faith (your truth) will succeed on merit.
However, if there is a kernel of doubt in your faith, you must overcompensate both in the number of people and their fervency. Only zealotry and sycophancy can quell the occasional contradiction and squeamish dissenters. Your faith will succeed on tyranny.
Naturally, this simplification highlights the success of bad ideas and the failure of good ideas, but more importantly, is to consider the idea itself shifts over time to a new set of values carrying the faith but weaponizing it and deteriorating the founding principles.