This is an appalling set of cherry-picked statistics.

There is no objective definition of what "upper middle class" even means, so one publication saying the ratio of people in it doubled is pretty meaningless. But even if we take it at face value, what does the rest of the population look like? The rest of the middle class must have shrunk, right? What happened to the number of people in poverty over the same time period?

Your second and third points appear to be offered in order to suggest "you too can be a rich easier than ever!"

The problem here is that the entire population is not moving up. Both income and wealth inequality are accelerating. The middle class has no more wealth than they did 30 years ago (and only modest increases in income), and the ratio of the population in poverty remains flat.

What you're seeing by this apparent increase in the upper middle class is the dredges of wealth concentration making its way up to the top 1%, at the expense of everyone else. This concentration of wealth has been happening for years. The rich are getting richer. When is the "trickle down" supposed to happen? If letting rich people keep more money is supposed to benefit everyone else, shouldn't that have happened by now? Or are they not rich enough yet?