Animals need cholesterol for their cell membranes; particularly for neurons. It's a precursor for Vitamin D, testosterone, and estrogen and is needed in the blood to help transport fat-soluble vitamins (A, D, E, K).

It doesn't seem at all strange that there should be an optimum level that is non-zero.

People brought into mental hospitals after trying to commit suicide have been diagnosed with very low cholesterol levels.

The body sythesizes sexual hormones from cholesterol.

When you do your study without accounting for treatments that are given to people with high risk of disease and which reduce cholesterol, you will find that lower cholesterol corresponds with disease due to those treatments. In other words, they have performed a large study that is likely to be confounded by indication.

I remember back in the 1980s that the Japanese researchers, whose population has (had?) very low cholesterol, were arguing with the US researchers, saying that cholesterol too low was bad as it led to (perhaps allowed for) strokes- which was one of their young-people-killers.

Odd? Odd because we've been taught what are amounting to myths[1] about cholesterol. Afaik, humans - especially the human brain - need a healthy supply of cholesterol. You literally can't think straight without it. And how many people are being pumped with statins?

[1] https://www.nytimes.com/2016/09/13/well/eat/how-the-sugar-in...

Like most things which your body needs (or produces from other materials), moderation is likely better than an outright deficit or abstinence.