Probably because FB is politically charged, disliked by both parties, consumers and the wider industry. The fine represents the public's anger at large.
Let's be even more honest: if they did know what Equifax is, what they do, and how long they've been doing it, they would certainly hate them more than Facebook.
Looks like you got downvoted a bit on this, but it's an excellent point. I fully think FB deserved what they got, and would not have balked at more. But Equifax, even with a fine higher than FB's relative to market cap, still seems to have gotten off lighter.