Movies used to be in theaters for weeks, and small indie movies used to have "viral" recognition. A basic website maybe with media, word of mouth. We didn't have YouTube trailers. These were movies that we saw trailers for during a movie or word of mouth got us there.
2 specific examples stick out to me. Blair witch project was a cultural phenomenon. I remember my dad wanted us to see it so bad and the theater by us was the only one showing it. Guys were in the parking lot selling their tickets to the highest bidder.
Paranormal activity was the next one. It started as a low budget , minimal screen showing movie. One theater was showing it by me, so me and my ex went 3 hours early and they were sold out. This was before online sales.
They don't make movies like these anymore. We used to be naive enough to think it was real. And even then, no CGI was used. Just plain camera tricks. Take me back.