That's not what preload is for. You don't wait for the extra images on the first page. You start loading them after the page is complete, so that the next page loads faster.

I'm not sure there was a technical way to preload back then.

I wasn't working in web dev in the early 00s, but I had done some informally. I just don't think preloading was a thing.

It's been a long time, but I'm pretty sure AJAX does not predate this website, SPAs were impossible, etc. I suppose you might do something with IFRAMEs, but you likely wouldn't be able to fetch those /after/ the main page. Preloading would be simul-loading and lag the hell out of your main window.

The way to instruct a browser to load back then was to wait for the user to actually click to fetch, and that would navigate away from the current page.

Dial up was 4 (four) kbps. Conceptually preloading wasn't possible I don't think

Very early, sure. But the later common speeds that most people experienced were between 14 and 56kbps.

Preloading was definitely possible even with just image tag ordering.

So people waited for 20 seconds to load each page?

Yes. The tolerance for slow-loading pages has shrunk dramatically since the early days of the web. Admittedly, 20 seconds was pushing it and people tried to reduce image sizes and such things to make it faster. But I recall in the late 90s, when I was selling CMS software to IBM, they had a rule that all pages needed to load within 3 seconds, and that was considered fast in those days.

I waited 4 hours to watch the 3min Phantom Menace trailer when it dropped.