Alright, so before I explain this you need to know the difference between exponential and gradual. If you already know the difference, skip the next paragraph :)
Gradual is something that happens steadily. Try and think of a collection. If you add one thing to it a day, then it gradually builds up. It’s even and increase always happens in count of “plus one”. Exponential is more chaotic. Instead of adding one thing a day to your collection, you build up QUICKLY. First maybe one, then seven, then eighty, and so on. It’s quick and always happens in count of “plus wayyyy too much”
Now that we established the difference between the two, we can go into why information spreads exponentially. Think of a virus: If one kid gets the flu and passes it on to three more people, then you have four people with the flu. If those four pass it on to three MORE people, then it’s sixteen kids that are sick. This is similar to how information transfers. No one is watching the news by themselves, no one catches the flu one at a time, everything happens in more than count of “plus one”
I hope this helps! :)