>what the hell was “protect Grandma” then? A hopeful wish?
It was an accurate assessment of the benefits of the vaccine, which prevents the worst effects and dramatically reduces the risk of death from infection. The vaccine was never intended to prevent initial infection, so they had no reason to delay it's introduction testing for that.
My wife's parents are in their late 70s with many health problems and got Pfizer here in the UK in the first wave of vaccinations. They both later got the virus and had barely noticeable symptoms. Sure it's possible that might have happened anyway, but I am confident the chances they would have died or been severely ill were dramatically higher if they hadn't been vaccinated.
Still of course even if you had spread disinformation about the virus, misrepresented the facts, claimed that it was supposed to do things it wasn't, falsely implied that it had no value even if you actually knew perfectly well what it was intended to do and that it did it. Even if you knew that spreading such misinformation would be likely to cost lives. Even then, no matter of how low my personal opinion would be of you, no you shouldn't go to jail for that. People listening to such claims have an obligation to educate themselves and come to their own conclusions as adults.