Big companies go after niches all the time. Many microbrews are owned by massive multi-national breweries. Huge drug companies chase niches every day. Giant food companies release ethic niche foods every month.
Whomever told you that there isn’t big money in niches or that they’re not worth going after is someone you should stop taking advice from.
AB Inbev, et al isn't targeting a niche by buying microbrews, they're building a portfolio that gives them access to growing and profitable craft brew market that's 1/4th of the total US beer market.
Retail dollar sales of craft increased 8%, up to $26.0 billion,
and now account for more than 23% of the $111.4 billion U.S. beer market.
https://www.brewersassociation.org/statistics/national-beer-...Google isn’t really in the business of filling small niches. That’s why they kill so many products that have small but passionate user bases. It’s just not worth their time and money so they shut the products down. This is why I can’t see them trying to start with a small social media niche and slowly expand to a bigger market. It’s a great idea; but seems to go against everything they do.