We're talking about a 20-year-old operating system here, what motives could one possibly have? Classic MacOS never had widespread malware to the extent of Wind

We're talking about a 20-year-old operating system here, what motives could one possibly have? Classic MacOS never had widespread malware to the extent of Windows worms like Melissa or ILOVEYOU, a claim backed up by your link. It's very plausible that the reason for this was that with far more users, Windows was a more attractive target. There is a reason that Bill Gates wrote the Trustworthy Computing memo and not Steve Jobs. (I doubt MacOS was actually more secure by design at that time.)