The danger of the covid virus was concentrated in specific demographics such that a lot of people didn't directly see how dangerous it was. This created a disconnect between what was being reported vs what people saw with their own eyes, creating the perfect environment for conspiracy theories to run rampant. For example, I don't know anyone that died or had a bad time with it, nor does anyone else in my family/close circle. But that's because I don't really know any old or medically vulnerable people, but with our aging populations in the western world this group is actually huge. We had people dropping like flies in certain sub-groups while in others nothing much happened and only where the groups intersected was it visible how bad it really was (healthcare workers, people with old grandparents not taking it seriously). It also doesn't help that older demographics almost always have something else wrong with them and Covid a lot of the time was one contributing factor that pushed them over the edge, this really fueled the conspiracy theorists narrative of falsely attributing causes of death to "inflate" numbers.
I also think the media took a wrong turn in it's messaging and told too many noble lies. It was really important that the young and healthy also thought that this might be real threat to them personally so they'd actually take it seriously and stop spreading it. But young people would lookup the statistics for their own risk and would see fatality/complication rates of sub 1%, and also note that those affected were primarily the morbidly obese and immuno-compromised. I recall seeing a lot of articles indicating that there was a surge of young people in ER and articles showing obituaries of young people in order to hammer home the message that it was a real danger to them too. The problem is the official statistics didn't back that message up to the degree that it needed to, so you had this big disconnect that was exploited heavily by conspiracy theorists. IMO this was likely a misguided effort directed towards reducing spread, because it was determined that quarantining to save other people wasn't a strong enough incentive to curb risky behavior (which is depressing), but backfired heavily and likely caused more harm than good.
If a more serious virus came around that had fatality rates in the double digits, I don't think conspiracy theories would be able to form. Because very quickly people would see people they know in their lives dying/becoming extremely sick. There's no uncertainly/disconnect to exploit in that scenario like there was with covid.