I think a major caveat here is there in science there is a big difference between "We don't have evidence that X happens..." or "In this study we didn't find that X happens..." and "X doesn't happen". The former often get converted into the latter. If we take masks, for instance, the guidance was really "We don't have evidence they will help so maybe don't bother", later converting into "Actually new evidence suggests they will help, so wear one", because we had a clearer idea what went on.Do a search. That the virus could not come from a lab. That bats weren't in the lab (they were). That the US didn't fund that lab. OK we helped fund the lab but not to do gain of function research, etc. Masks won't help. Mask are mandatory. Non-vaxxed spread the virus. Oh. Even the manufacturers never claimed vaccination slowed spreading. It has been a #^%$#^ show.
That said, it is very possible that the government deliberately fudged on the initial statement when they declined to recommend masks. The potential reason being, there weren't enough masks: if they said masks would help prevent infection, people would have panic bought masks, and the health service which needed them most would not be able to procure them. It doesn't matter how much you tell the public "You should try to mask up, but please wait a month or two because supply is limited and health workers and the vulnerable need them most", people will panic buy and leave the health service and vulnerable people short. Literally every time the government warns against panic buying, people panic buy and cause shortages anyway: it's just the way it is. The government has to deal with this. So if the government fudged information to try to protect the health service and ensure vital supplies got to the right places for maximum societal benefit, is this truly a bad thing?
Where there are a lot of unknowns so there is a lot of uncertainty, opinion of varying reliability, and confusion. The simple fact is that people will just tend to latch onto what suits them. People suspicious of government or China or science or whatever will just select out whatever narratives fit their preconceived notions. People who hate China are far more likely to believe the virus was brewed in a Wuhan lab. People who distrust vaccines tend to be people who most distrust the government and Big Pharma. People who oppose the usefulness of masks tend to be people who oppose the government insisting people wear masks. And where there is a lack of certainty, or at some level they realise they are on the wrong end of the argument, they blame the same people they always blame for that confusion, too.