No one said that though. What was said was that as more people use Linux we will see more malware. And they've been saying that forever.

Here is an article talking about it from 2003 https://www.theregister.com/2003/10/06/linux_vs_windows_viruses/

If I knew how to search Usenet these days I'm sure I could find something from the 90s

It's not untrue, actually, is common sense that there will be more malware, but it implies Linux's only advantage is security through obscurity.

People have been worrying Linux is going basically become Windows over the next couple of years for 2-3 decades now. Malware is a serious problem that Linux users should take precautions from, but it seems clear by now that what security advantages it has aren't based on obscurity.