Not surprisingly, people often confuse well spoken individuals with intelligent individuals. We've probably all met the incredibly polished and well spoken person who was otherwise dumb as a sack of hammers, but it took a long time to figure it out because of their well developed communication abilities sending a confusing signal.
It short circuits our intelligence detectors. It reminds me of Williams Syndrome which, despite sufferers having an average IQ of about 70, confound people who know them because of their high social engagement and constant friendly chatting.
I've found it's often helpful when meeting new people to sit back and observe the quality of the thinking behind their words rather than just the words themselves. The results are often surprising.