As for the confluence: I don't know the specific triggers, but I think that's a totally reasonable theory. I think we all have more resemblance inside the backs of our heads than we realize, so if something random in an episode of a popular show reminds me of a snack I used to eat after school, then even if it only has that effect in 1 in 100 people who watched the show and had that popular snack food when they were kids it could still suddenly create a burst of a thousand people googling some obscure 90's snack product the following week. I think that kind of stuff happens all the time.