Nothing so popular as goodness.
Franklin suggests that goodness has a broad appeal because people generally value qualities such as kindness, honesty, fairness and generosity in others. Someone known for good conduct is therefore likely to earn trust, respect or affection within a community. The saying links moral character with social approval rather than with status, wealth or display.
The statement is deliberately general and should not be taken to mean that good people are always popular or that popularity proves moral worth. Virtuous actions can sometimes be unpopular, while public approval may attach to people for reasons unrelated to character. Franklin’s broader point is that genuine goodness tends to create goodwill because its effects are beneficial to others. Reputation built on fair and considerate behaviour can therefore be more durable than approval gained through appearance, influence or self-promotion.