The expectation was that because they knew the vaccines reduce the chances of getting symptoms such as coughs associated with transmission, reduced the time people were sick for, and also reduce the viral load in people who got sick, that this would result in a reduced chance that people who caught the virus but were vaccinated would transmit the virus. It was an expectation, yes, not a proven fact but they thought it was worth working on that assumption due to the hoped for benefits. It turns out now, after extensive research on transmission by vaccinated people, that they were correct and vaccination does significantly slow transmission through populations even for the more recent highly infectious variants.
>I’m increasingly understanding why some folks are “paranoid.”
I really don't, all of this information has been available all the way through. That Pfizer executive was simply being honest, what the vaccines do and how they work and the benefits they offer has been accurately communicated right back from the trials phases. I know this because all through those times I kept myself well informed and followed the literature. It helps that my wife is a Nurse, and also that I'm in the UK where the whole issue was far, far less politicised and the accuracy and consistency of information from the media was actually pretty good.
The problem is there was an awful lot of disinformation going around in the US from people either getting partial information and making wild unfounded assumptions, or deliberately fomenting opposition to various policies on political grounds. Nevertheless as I said in my previous post, we're all adults. It's our responsibility to inform ourselves, we can't blame disinformation, some of which is genuinely simply mistaken.