Your link provides very little evidence for your claim.

What did you take my claim to be? The example in the link is intended to illustrate the fact that the problem of politics is not one of figuring out better policy. It is an example of a policy that is universally agreed to be bad and yet has persisted for over 60 years, despite a brief period in which it was temporarily stamped out. The magnitude of the subsidy in this case may be small but there are many thousands of such bad policies, some of much greater individual magnitude, and they add up. The example is intentionally a small and un-controversial example since it is intended to illustrate that if even minor bad policies like this are hard to kill then vastly larger ones are unlikely to be eliminated without structural reform.

None of them appeared to have the slightest interest in directly profiting from their work as public servants, nor in exploiting their positions for fame, sex, etc.

Giving this appearance is fairly important to succeeding as a politician so this is not indicative of much. I find it more relevant to judge by actual actions and results produced rather than by words or carefully cultivated appearances.

In my opinion, based on a moderate level of personal experience, the assumption that politicians are primarily motivated by self-interest at the margin in equilibrium is simply false.

As a well known politician once noted, you can fool some of the people all of the time.