What do you mean with "became bad"? It started out with a 140 characters limit in 2006 and kept that for more than 10 years. So its the other way around: it became worse, when the character limit increased. Though I don't think its due to the character limit either way.
It was bad long before they increased the character limit.
Saying shitty/toxic stuff can be done concisely. Giving a nuanced response is simply not possible. So people respond with jokes/sarcasm/counter toxic stuff. And the cycle continues.
Saying shitty/toxic stuff can be done concisely. Giving a nuanced response is simply not possible. So people respond with jokes/sarcasm/counter toxic stuff. And the cycle continues.