Experts are a real thing. People who spend a lifetime learning about something will, on average, make better decisions about that thing then you or I. Pretending that this is not true is not only silly, it's often dangerous.
I'm not convinced this is true. If you spend a lifetime doing something then I'd agree you'd be better than average at it. In such cases experts do not face much scrutiny, there's little doubt on a pilot's skill at flying a plane and no sane person thinks they are better at chess than Magnus Carlsen.
What is happening now is that we are taking people who have merely studied something extensively and asserting that knowledge gives them superior insight into decisions about the future. These "experts" might even be directionally right more often than an average person but that isn't enough. If expertise through a lifetime of learning leads to your confidence in your own abilities outpacing your actual abilities than they are going to make worse decisions than a lay person who is cautious in the face of uncertainty. Examples of this effect are abundant, the greatest team of financial experts ever assembled (LTCM) managed to lose every penny and then some while my parents 401k remained solvent.
There's good reason to believe a life insulated from the ups and downs of normal life leads to suboptimal risk judgement compared to a less educated person. There's a clear assymetry between overskepticism and overconfidence, the latter hurts you far more than the former. To suggest that skepticism is the more dangerous of the two denies the reality of most of the largest disasters of the last century.
...at the expense of things they are not experts in. Ask an expert in virology how to prevent spread of the virus and they will give you a good answer. But that doesn't mean turning their advice into a mandated policy will work out well. Game theory comes into play there and an expert in virology is likely not an expert in game theory, politics, economics, or anything else involving policies affecting 350M+ people.
To be fair, neither are most politicians.
One problem here is the conflation of government officials and academia with expertise. It's quite plainly possible to spend your life in academia yet end up with no actual expertise in the topic you're studying, as evidenced by the large number of papers out there presenting unvalidated predictions which end up being wildly false, over and over again. Fundamentally, in academia and government being wrong doesn't cause you to lose your job. Your job depends instead on your reputation and alliances. A large amount of groupthink and incorrect beliefs is a natural outcome.
This conflation doesn’t happen by itself. Who does this? What are their motivations for doing so?
The problem is it's not sufficient to have time and money. You also need to be in an environment where you're expected to deliver genuine truth, and there are rewards for doing so and penalties for not doing so. And in the public/academic sector these things are lacking, which is sufficient to overpower the specialising effect of full time employment.