I don't understand why people decide to be toxic.

I think you mean to link to something like this:

https://support.riotgames.com/hc/en-us/article_attachments/202395730/SS_Chat_Restriction_Notification_01.jpg

But the point still stands that the result is generally punishment :)

I'm a firm believer in that it's because the person has poor coping mechanisms.

However, people can learn and grow and become less toxic IF they choose to grow and try and learn better coping mechanisms.

Unfortunately a large portion of the people here that I see posting choose not to adopt new coping mechanisms and insist that the LoL community is the problem and not them.

people need to find a way to release their frustration

I'm not sure most people are even conscious about the fact that there is a choice. :/