1) the declarations that mailchimp and other big brands didn’t advertise. I have certainly seen ads of theirs, heavily promoting their products.
That’s true, you may have seen ads BUT I can guarantee that they grew thanks to their awesome product and word-of-mouth. The rest was here to support it.
2) a certain percentage of people do respond to cold emails and aggressive marketing.
Cold email doesn’t necessarily mean bad marketing (I have received awesome cold emails).
I guess it depends how you define “aggressive” marketing :)