When a Manhattan jury found Donald J. Trump guilty, it should have sent shock waves through the nation. Yet, though the trial and conviction of a former president was unprecedented in American history, it seems most people couldn’t have cared less. As Michelle Goldberg recently noted, only 16 percent of respondents to a Yahoo News/YouGov poll said they had followed the first few weeks of the trial very closely, and when asked how they felt, many replied, “bored.”In its way, that must have annoyed Mr. Trump: how insulting, that no one would care. There was media coverage, but no frenzy,...