Where individuals, groups, religions and, most importantly, nations, make their biggest mistake is in believing that since their aims are "good," then anything they do to achieve these objectives is allowable. This is the much-reported "The ends justify the means" approach that is responsible for half to three-quarters of the evil in the world (the rest being mostly just plain uncaring greed and/or ignorance).
When significant numbers of people adulate and aspire to be like those venal and rapacious individuals who get away with all manner of greed, duplicity and even violence in the pursuit of money and power, then that society has become decadent, and will fall.
Short and Sour
First comes co-opting, then comes corrosion, then comes corruption, then comes consequences.