This is a pure observational study:
Low total cholesterol is associated with increased major adverse cardiovascular events in men aged ≥70 years not taking statins
As such, let's generate an hypothesis.
Let's assume total cholesterol (TC) is utterly, totally and completely meaningless. About anything.
Let's assume that TC is a surrogate for "something" (Something Good) which is really important.
Let's assume that people with high TC are doing something right. Something which the study never even thought about, let alone measured.
Let's assume that statins do absolutely nothing (being generous).
Let's assume people only get put on a statin if their TC is high, ie, they are doing Something Good.
The Something Good behaviour pattern persists despite the statin.
The statination makes the TC number decrease, which makes the statin victims look as if they are doing the Something Bad which, obviously, lowers your TC. But they're not. They do well despite the statin and despite the artificially lowered TC.
EPIC Norfolk suggests looking at HbA1c if you want to look at cardiovascular and all cause mortality. Hints about Something Good here in Norfolk?
Edit: No one (least of all me) would suggest HbA1c elevation is causative of all cause mortality. But at least it starts you looking at the correct metabolic pathways! End edit.