There were news reports that Russia spent less than a million dollars on a massive propaganda campaign targeting U.S elections and the American population in general.

Do you think it would be possible before internet, before AI?

Bad actors, poorly written/sourced information, sensationalism etc have always existed. It is nothing new. What is new is the scale, speed and cost of making and spreading poor quality stuff now.

All one needs today is a laptop and an internet connection and a few hours, they can wreak havoc. In the past, you'd need TV or newspapers to spread bad (and good) stuff - they were expensive, time consuming to produce and had limited reach.