The event was played 11-14 September, and is documented on the official site, Champions Showdown: Chess 960 (uschesschamps.com).
Here's a video from the Saint Louis Chess Club.
2018 Champions Showdown: Kasparov’s Interview - Day 4 (7:40) 'Published on Sep 16, 2018'
The description says simply,
Grandmaster Garry Kasparov shares his thoughts after his games on Day 4. He has lost to Topalov. 2018-09-14: USChessChamps.com
The date pegs the video to the last day of the Showdown. Before the games the players had time to analyze the start position selected for the game. GM Kasparov said,
What happened today, I still can't find the explanation. We spent 29 minutes with Peter [Svidler] analyzing a different position. [...] I don't want to spread blame, but actually Peter looked at the position. It's my fault; you just have to look at it yourself. [...] One shift and everything's different. Absolutely everything. It's not that you can reuse the patterns. Absolutely everything changes - the geometry, the structures, the way of developing the pieces. If I hadn't looked at the position at all, that would have been better.
The former World Champion donated his $20.000 prize to chess in Africa.