I think that just happened.
I like how everyone is just reacting to this without providing any goddamn context, as though we're all supposed to instinctively know what this is about.
Kimmel does this segment where he has celebrities read derogatory tweets about themselves.
Does he realize that the person behind that Twitter account is dead? Because this just looks like it's part of a larger bit; not that he's specifically honoring Ryan Davis on live TV.
They likely have no idea. Nothing about Ryan's Twitter account indicates his passing. Whoever decided to use the tweet probably just did a general search for Mark Ruffalo-related tweets and found that one among the more amusing.