To the stoics themselves, wealth and power are indifferent: neither good or bad.
I say that the title is provocative because wealth and power often provoke people, as can be seen in this very discussion (here on Hacker News). Depending on where you come from and where you are in life, a phrase such as "rich and powerful" may call forth the negative stereotype of evil wealthy people, or it may call forth the positive stereotype of Hacker News style entrepreneurs.
It is much easier to be indifferent to wealth and power if you already have it.
My take on the supposed rise in popularity of stoicism is not that it appeals to the "rich and powerful" per se. I do however think it appeals to people who have found themselves in a situation when they no longer have obvious things to live for, which is certainly the case for these people.
If you suddenly find yourself with free time and autonomy, philosophy is a pretty good thing to fill the void with, I think.