[Sophira]

The problem is that the DIV that contains the main text has the attribute 'style="opacity:0"'. Presumably, this is something that the JavaScript turns off.

A lot of sites like to do things like this for some reason. I haven't figured out why. I like to use Stylus to mitigate these if I can, rather than enabling JavaScript.

[acdha]

This is a common anti-pattern — I believe they're trying to ensure that the web fonts have loaded before the text displays but it's really annoying for mobile users since it can add up to 2.5 seconds (their timeout) to the time before you can start reading unless you're using reader mode at which point it renders almost instantly.

[MattRix]

The page animates in. I have no idea why it does, but it does, which explains why the opacity starts at 0%.

[ectopod]

A lot of these sites (including this one) do work in reader view.

[test1235]

mitigation for a flash of unstyled content (FOUC) maybe?