Look, if the malware spreads by users manually installing it, 1. it's not really an OS problem, 2. an AV wasn't going to save them.

That's how almost all malware was installed though. Linux really isn't any more resistant to malware than anything else.

Really depends on ecosystem and time; I remember when connecting an unpatched XP box to the internet got it infected with zero user interaction.

Within minutes, sometimes. You couldn't even go online to get the updates if you didn't have a firewall.

You would be wrong!

https://en.wikipedia.org/wiki/Linux_malware

Yeah, sure, until you open your browser and start installing all the crap like crazy. Because even 'legitimate' software can give you nasty adware today in software installers. And lots of adware isn't tagged as malware.

Both Windows and macOS have binary whitelisting in place making it harder to run arbitrary binaries that aren't known good to the OS vendor. Pain in the ass sometimes because Windows Defender quarantines executables and DLLs I freshly compiled, and you have to do command line magic -- after every update -- to get unsigned stuff past Gatekeeper and Xprotect, but in terms of endpoint security for normies both Windows and macOS are way ahead of Linux.

I repeat: a lot of installers from good companies bundle adware which might not be malware but turns your i5 machine into a Pentium II, which in the end it's the same.