Basically just an evolution of the same way I used my desktop 20 years ago. Always had this concept of an Internet-connected computer as a dynamic newspaper, windows were individual columns arranged around the page/screen. Used to be a bunch of IRC windows along the bottom of my screen, maybe a couple of MSN windows up the side, and one or two browser windows (substitute one browser window with an email client or RSS reader) taking up the rest of the screen.
Well now everything is javascript. Google had the same idea with Google Wave a few years later, they abandoned it, but the javascript future happened anyway. Bunch of tiny browser windows along the bottom of the screen for discord, two large ones across the top for everything else (webmail, content aggregators like lemmy have largely replaced RSS), and a couple more on a second monitor.