speedtest.net, as you know it now, was only started in 2006.
source: wikipedia speedtest.net
Wonder why their results favor the ISPs... One has to assume cronyism. ...they weren't chosen for accuracy.
So you see... the speedtest.net you saw in the 90's was someone totally different. It was bought and converted in 2006, almost instantly was used by every ISP. ... even though it was common knowledge among computer nerds/geeks/dudes that it was complete BS.
Wayback machine only goes back to 2000. Here's a funny screenshot.
But yes, even the version before ookla stepped in required plugins to work. I've never required plugins.