The ladders only go down to 1200... so yes they do not show extremely low rated players. In game you can only see peoples rating if they are 1250+. The being said trolls exist at almost all rating levels... I still seem them at my rating which is 1400+ usually.
It is somewhat the players fault for being so low, but also the fact that at those ratings you literally have to carry so much dead weight to attempt to get anywhere. I am happy to say I have never sunk quite that low; and it is unfortunate that people above bronze are actually pretty rare especially in solo queue.