You don't have max-width set on the text, so unless you have your browser window resized to very small size the paragraphs will span your whole screen.
Which places you, the reader, fully in control of the width of lines you prefer to see. Adjust your browser window width, or apply a user style sheet to tell your browser to format the text the way you want to see it formatted.
I knew this reply would come... How many people do you think use custom browser stylesheets? It's probably smaller than 0.1% of the internet population and everyone moved on to formatting text so everyone can enjoy good readability. Also not all devices have the luxury of supporting custom stylesheets.
Of course it's always up to the site owner, but most people want people to read what they share.
I see. I don't have a wide-screen monitor (still using an old tube type until it finally expires but it's taking a few decades, lol). I've wondered whether people actually like reading websites on wide-screen. Some do and some don't. What would you suggest for a max width?
You could also try zooming in. My apps don't expand to full width because of the video box but you can zoom.
I have the opposite problem. I typically have many browser windows open at the same time but only two screens, and many sites that I use are designed to assume that everyone has full-screen browsers.
Similar problem here. My resolution is 1440x900 (27in Monitor) paired w/ 1280x720 (32in TV) and I keep 3 Browsers Open (Edge, Opera, FireFox - each has intent). Each are at 3/4 width and 1/2 height and offset so I can see each partially.
With this setup, many sites work, but a few... a few have a top ad banner, a side banner and a footer of 'cookie acceptance'... then add in a 'subscribe to our email' and a google login prompt.... (Game Wiki's.. I game in smaller windows too -- what good is a multi tasking computer if you don't use it?)