Most people wanted to play solo anyway, but couldn't even do that due to the inadequate server capacity.
Citation needed here. Honestly, Diablo is really boring if you aren't playing with other people, it isn't really much of "experience" without loot trading and fighting stuff together. I can't imagine that people wanting to play alone and never use any of the online feature are anywhere close to the majority. Frankly, I wouldn't have bothered playing it on day 1 if only single player sandboxed characters worked. I would have just waited.