Everyone is ever so slightly telepathic, functionally making a web of felt emotions with no thoughts connecting them so what you feel from this is basically a summary of the people in the area around you.
Example: Everyone could be focused at work, nothing major going on, until someone thinks about their significant other and all of a sudden there's a tiny bit of horny thrown in the mix, everyone knows its there, and no one knows who put it there.
And thus, entropy is presented. Even if only 10% go to Firefox, thats still 10% that aren't going back to Chrome. And if this repeats with similar results, as you imply, that 90% going back to Chrome is gonna be a lot smaller a few iterations from now.