[Brainstrom] Why is about.com losing in search rankings?

I was looking at organic traffic for some top sites which largely depend on organic traffic.

About.com is one of them and I noticed that they are getting less and less of organic traffic every month. From over 100M in Feb 2014 to 30M in August 2015 (source SEMRUSH)

Which brings me to the question: Why is about.com losing its ranking?

Anyone willing to brainstorm with me.

Because competitors are buying better and more links.

SkyrocketSEO said:

Because competitors are buying better and more links.

Click to expand...

So linkbuilding efforts of competitors could be a reason but such a systematic decline in traffic indicates otherwise. Especially considering about.com is in all niches, if some niche competitors is buying links traffic in one or two niches should decline not across the board.

who cares, honestly

The answer is easy, their website is no longer favoured by search algorithms