They couldn't figure out why. They almost rolled back the change until someone figured out the reason. Millions of users with very slow internet couldn't even open YouTube before the change. Now, they could.
Tesla probably weren't tracking store visits, and test drives in relation to online purchases. And this missing info misled them.
http://blog.chriszacharias.com/page-weight-matters
Edit: Changed 20 minutes to 2 minutes. After rereading the article.