The answer to these questions may be a a simple one, this being the mere fact that Barstool pays attention to their customers and what they have to say. Barstool has a huge social media presence, specifically on Twitter. Every member of the Barstool team utilizes Twitter, interacting with fans from common men to professional athletes. Dave Portnoy (President of Barstool Sports) often uses Twitter to convey company information to customers as well as receive feedback from them.
Portnoy tweeted this on September 8, 2015 regarding a potential new T-shirt idea. He received positive feedback from customers on Twitter, getting well over 300 retweets and over 1,300 favorites on the initial tweet. Portnoy ended up making the shirt and sales have been great. Customers often tweet pictures of their order or of them wearing the shirt at Portnoy and he also does a good job of getting free advertisement by retweeting them.
Further evidence that suggests Barstool Sports uses sources of primary data like social media is an article done by Adweek on September 21, 2015. This article listed and reviewed the top-ten media publishers in the month of August. While Barstool Sports didn't quite crack the top-ten, they did make an appearance in the article:
"Barstool Sports saw the highest growth of any publisher in the month of August at 125 percent."
Adweek measures social actions which encompasses all sources of social media, including Twitter, Facebook, Instagram, Youtube, etc. It records things like tweets, retweets, favorites, likes, shares, comments, among others, and measures each company's growth over time. Not only did Barstool Sports record the highest growth rate in the month of August, they recorded the highest growth rate of any month ever. This is a very impressive feat, and shows that the already popular company is still on the rise.
To summarize, Portnoy and the Barstool Sports team are able to use social media to interact with and receive feedback from their fans. They use this primary data to make business decisions to benefit their company and increase sales. Utilizing social media is a very inexpensive way to advertise, but can be quite effective when used in the right ways.