In both cases, it wasn't the original message that kicked off the firestorm, it was a deliberate strategy put forward by billion-dollar presidential campaigns.

Nobody knew about the "eating my neighbor's cat" post even after the debate. It took weeks to track down what Laura Loomer had whispered into Trump's ear. Nobody considered the "Hillbilly Elegy had a chapter where Vance fucks a couch" tweet important until celebrities and politicians began retweeting it as a means of disgracing a weird conservative sex pest.

If there's a rumor started by a smear campaign run out of an office in Moscow (and they're even halfway competent in their execution) you're likely only going to hear about it once it becomes the focus of some rhetorical exchange-of-fire on a top tier domestic social media celebrity or in a Senatorial debate. Even then, you won't get to hear where it originated from until the polls have long since closed, in much the same way nobody got the details on the Comey indictment of Hilary or the Georgia election-steal attempt by Trump until it was too late.

It isn't "one person" starting a rumor. Its an industry that feeds on rumors and is constantly regurgitating them to get your attention.