Why do some sites spam the index when searching info?

Let's say when you search info/reviews for some sites like for example City Data to see if it's reputable or Debate.org which I've never heard of until it came up on a question I was asking about politics

How come all I get is links to their address instead of what I search for? It's almost like they ahave fond some way to flood the index of nothing but various links to their site.

I've also noticed this never used to be a trend until the 2013 algorithm updates and now Google is worse about spam indexing. Is there even a word for it?