Sounds like that was more of great product than a successful advertising campaign, even if it did help.
With regard to niches, my experience has been the opposite.
If your niche is small enough, you can't properly bid on adwords for rare keywords because they are flagged as "low quality" and you are forced to either abandon those keywords or pay 10x for them to show.
This, of course, defies the entire raison d'etre of adwords - the whole purpose of which is (presumably) to bid on a keyword that targets that one rare person that searched for that.
But it can't be done - if only 5 or 10 people search for a phrase or keyword every day, it cannot be bid on properly.
Alec Brownstein did exactly that by ad targeting his favorite creative directors' names some years back in order to land a job. It worked.
https://mashable.com/2010/05/13/job-google-ad-words/#GvW9atl...
I was faced with keyword combinations that had "natural" costs that were very low (and appropriately so, since I was the only person "bidding" on them). But then a few days later, "low quality score" and they ratcheted up the price 10x.
If you get a job out of it, the penalty doesn't really matter ... I was trying to convert $5/mo IaaS customers.
How do you define a great vodka? With blind testing?
If its like beer, then there's a few types of beer and perhaps some spice but its mostly the same.