I've always seen world champs (and of course diamond league) as far more competitive than the Olympics.
Because they're every 4 years, the field in the oly has a lot of churn: the on-form guy 2 years before the olympics has more chance of getting injured / have a bad selection race / losing shape of momentum for any reason in the run up to the Olympics. It happens really often. Preparation over such a long period of time is really tough.
There's also lots of pressure on the athletes during the Olympics, so they tend to run tactical (dare I say boring) races to avoid throwing away 4 years of training in a bravado move. That's understandable but it also lessens the value of the Olympic gold, where athletes are theoretically expected t provide their best effort (for the whole race).
But back to the main topic, a world record is based on the notion of best effort. In fact of best effort ever. It is painful, unique, unreachable at the time and (except in doping cases) unquestionable.
An olympic gold defines the best athlete, in a particular field (not necessarily the fastest, or the deepest at the time), and with particular race conditions (not necessarily the best effort). In tactical races, even if a winner is clearly identified, there are still doubts whether this winner is really the best at the distance.