SNES didn't have online capabilities, it had satellite capabilities with specialized and expensive hardware (assuming you're referring to SatellaView).

Anything that requires specialized hardware to access the internet isn't ready for general consumption.

PSOepIII (episode III, not PSO III. It was actually PSO II) was an MMORPG; MMORPGs are aimed at a far different demographic than the group that the Wii was targeted at. Also, weren't PSO ep. I and ep. II released on the GameCube? Pretty sure they were.

"There were multiple companies in the 60s that had mainframes that didn't even work very well; are you telling me that your average family wouldn't be ready for computing back then?"

Focusing on internet connectivity on the Wii would have harmed the Wii, yes. The Wii had Wii Shop and a few titles that could interact online. Making it the core feature in many of them would harm the console, because not only would many people have difficulty setting it up, there were also significant portions of even the United States that were almost entirely decrepit of even moderately decent internet connections.