Where are your commenters? This is a good overview and a history lesson for the younger techs for sure.

I am old enough to remember them all. I think ICQ was big because it had a nice light-weight (yet pretty) client for private messages and status updates. I guess that's the power of UI. I started using it because the gamers took it on.

Today Discord is #1. It's not on your list, but maybe it's just the latest iteration of chat. Again, it was gamers who drove it's adoption IMHO.