Why would the cigar seller ask to show me an ad for a STOP SMOKING CIGARS product? Also as I said, this showed up in Youtube the day after I ordered and the email hit my gmail. Never seen those ads before.

The cigar seller sells its customer list to a data broker or uses a third party service that does the same (e.g. it uses your email address as a user identifier in a third party analytics product). Then advertisers buy that data.

The sold it in less then 24 hours?

Well, it's not like they need to ship the list of email addresses across the company in a truck.