It’s called GoodNews WordPress Theme
It’s from ThemeForest.
Surely WordPress can do something to aid with this issue though. Even if it is a theme. It’s a theme that runs in WordPress. Ultimately if wordpress implemented some way to prune or stop excessive images being created by a theme… Problem solved.
I’ve had this issue multiple times and it could be there are many many many themes and plugins that create this problem. We need a fix otherwise files sizes will get out of control. Backing up and transfers will become an even bigger nightmare than it already is.