There is a decent talk "Big Fat Fiasco" (about an hour long) that explains what happened with nutrition science.

Some of the interesting parts are near the end of part 2/start of part 3:

Specifically senator McGovern dismissing complaints from scientists that there was not enough evidence that fat caused hear disease by saying:

Senators don't have the luxury that a research scientist has of waiting until every last shred of evidence is in.

A little latter the video mentions that at the time 90% of all funding for research on heart disease was provided by the US Government and American Heart Association. Thus once both said that fat causes heart disease it was nearly impossible for scientists who got conflicting reports to get funding.

Edited conclusion to make it clearer:

There are two problems here:

1) The attitude that this area is too important to wait for "every last shred of evidence" and thus we must go with science based upon weak evidence.

Where else have I heard this, which appears to be prevalent in climate science and pandemic medicine today.

2) Nearly all funding provided by a few large organizations that are thus subject to politics and group think.

This appears to be true in most sciences today.

As such, unfortunately, it appears the case nutrition science isn't just an isolated incident.