Both of your examples have a very strong technical component, either understanding the underlying biology/epidemiology or understanding war theory and practice. It is indeed unlikely that someone is an expert in both.
But many important topics have far fewer, if any, objective truths attached to it. In the case of covid restrictions, opinions should obviously be founded on science, but science can only inform our moral choices, not make them for us. Is the damage done to developing minds worth locking down schools if it reduces the spread of covid? Can there be a state/societal mandate to force people to stay in their homes, or even to get vaccinated?
You can come to very different conclusions based on how your worldview is constructed, and I think the sign of a true intellectual is that they can coherently describe theirs, and make other intellectuals understand it, even if they are diametrically opposed to it.