I could agree with that if price was weighed in as a factor. I don't recall the prices of the Vizio but I do seem to recall them not being bad for the money.
What we really should be asking ourselves is why in a world that vastly moved from desktops to notebooks for traditional PCs, and a world where the traditional PC sale is dwindling are companies now seemingly making a lot more AIOs when that was previously just a stupid Apple thing? From a personal standpoint the iPad and iPhone have made want a desktop again, but one that doesn't have all the wires of a traditional setup.
I think the answer is the same as why laptops became very, very popular. The old tech didn't have the lithium-ion battery life, nor did it have the processing power of today's machines. The same to be said for the mac-mini designs, all laptop hardware based. The G4 was a slug, although great at the time for dorms and apartment dwellers who only needed to write papers and email. Gaming on a G4 mini was laughable. Not the situation anymore with the advances in technology.
The capability of today's machines allow for such designs to exist, in other words. AIO's are coming around to the forefront because they are taking up the top of a small desk, rather than a huge desk with a "cubby" for a separate tower. The graphics cards in the AIO's coupled with the decrease in heat from the CPUs allow them to be just as capable as the old tower design. In short, you can have both processing power and excellent gaming experience on a much less intrusive footprint now, whereas 5 years ago this wasn't possible.