https://www.youtube.com/watch?v=7jUeifzCIlU In the first few seconds of this ad promoting a TV show, the narrator is saying 実況してみた. I looked up 実況する and see it means 'live broadcast', so does it mean 'watch live'? But in that case, why is 見る in past tense short form rather than て form?
みた in 実況してみた means try to do or try doing something.
In the phrase, 見る has almost completely lost its original most familiar meaning, but supports the verb 実況する by adding the meaning of an attempt or try.
As for this particular usage of 実況してみた, I assume this is more about online subculture than language.
The widespread online use of 〜してみた, such as 踊ってみた, I believe, has originated in Niconico, a popular hangout among manga and anime aficionados. Now, 〜してみた is more widely used online, and often appears in the headlines of videos of amateur YouTubers.