In judging the electoral college, how important is it to know that on several occasions an elector broke with custom and voted independently

An elector has a pledge to vote according to an agreement. If the elector failed to vote the candidate they pledge to vote, they are now called faithless elector. However, based on the study faithless electors are a few and had not affected the voting process. Still, this only shows that they don't keep their pledge and do not trust the candidate that they supposed to vote.