The content is created by volunteers. But fandom is a for-profit company. In its early days when it was known as Wikia, they maintained a fairly small team of people running the site. So they just had to make enough money for paychecks and bills. Here's my take on what went wrong. Throughout the years they grew. Because the company grew, they hired more hr people - more money needed. So they hired marketing teams, data science and so on. The costs skyrocketed. So now they're putting ads everywhere because they don't have that much more traffic than 10 years ago but the company is much larger.