Requests are not all equal. This page loads one deliberately large image. Watch the Size and Time columns, and notice the picture appears a moment after the text.
big-image.html — about 2 kilobytes, arrives instantly.photo-large.png — about 1.8 megabytes, roughly a
thousand times bigger.
The text was readable before the image finished. That is because the browser displays the HTML as soon as it has it and keeps loading the picture in the background.
In DevTools, find the No throttling dropdown and choose Slow 4G, then reload. Everything slows down, but the big image slows down the most. Set it back to No throttling afterwards.