OK, so it is obvious that SOMEONE is carrying on an astroturf campaign. But how do we know definitively it is Maddow? It could be a fan. It could be someone at MSNBC, but not on her staff... short of MSNBC and/or Maddow admitting something, we really have no proof it was Maddow that did this.
It’s spamming. What they probably did was hire it out. Googling “twitter accounts for sale” shows a bunch for sale on ebay.