Paragraph 1: In 2004, three PayPal employees had a light bulb moment. Chad Hurley, Steve Chen, and Jawed Karim envisioned a place on the internet where people could share their home movies with the world. They set up shop in a Silicon Valley garage, and Karim posted the first ever YouTube video in May of 2005. “Me at the Zoo” was just 19 seconds long, and it featured Karim casually speaking in front of the elephant enclosure. The video bore little semblance to the sophisticated productions often seen on YouTube today. In 2006, Google acquired YouTube for $1.65 billion. If the original YouTube founders had had a crystal ball, they might not have been so quick to sign on the dotted line!

Read this sentence from paragraph 1 of "YouTube: A World of Knowledge and Fun at Your Fingertips."

If the original YouTube founders had had a crystal ball, they might not have been so quick to sign on the dotted line!

The phrase "had a crystal ball" refers to the YouTube founders ​

being able to see into the future and predict the enormous success and impact that YouTube would have. It suggests that if they had known how popular and profitable YouTube would become, they may have made different decisions regarding the sale of the company to Google.