No one should accept this as an excuse. They weren't rational, they chased the shiny.
I'm not sure "visibility bias" already has the right meaning, but if not we need a term for this pervasive problem where people just choose to not believe or otherwise ignore factors that don't leap out to them, even if they're just as if not more important in reality. More abstractly we see it with Alzheimer's hypotheses here: Hypotheses with greater uncertainty suffer the same treatment, where not having as clear an idea about what it is causes it to be entirely discounted, for years, in favor of the clearer action plan.