Generally, there is just a high concentration of toxic players in this tier.
If something goes wrong in the early game (i.e. a lane dies 1v1 to their opponent, an ally does something they disagree with), it is not uncommon to see players begin raging at one another or want to forfeit the game within 5 minutes of starting.
In addition, many players are rather set in their ways and refuse to admit that they may be doing something wrong. People will continue picking bad fights and feeding their lane opponent, they will constantly group or refuse to group without considering the situation and everyone thinks they know best.
It is just a horrible ranking to play in. I found the players in Gold were much nicer to play with and against since there was less general toxicity.
If you want to see an example, I would recommend watching a few of HuzzyGames' Unranked to Diamond videos on Youtube from the past few days.
They demonstrate what I mean rather well.