A few days back, someone on Twitter highlighted that viewing a single image on Imgur causes downloading and running a megabyte of React first. The consensus in the thread was that the engineers at Imgur need to be morons in order to let something like this happen.
My take on this is that it has grown organically. Imgur is not interested in making the mobile experience (that’s what this is about) great, they want you to use the app instead. Coincidentally, the “Download the app” button is among the first elements to be rendered. My best guess is that the current mobile page is just something cobbled together on top of old software, with the business people breathing down the developer’s neck.