The New York Times reported that the list was criticized for not being diverse enough by the National Association of Black Journalists and Univision. While one of the presidential debates has a woman moderator for the first time in 20 years, all of the moderators are white.
While Raddatz and Crowley are new, Lehrer is a veteran of 12 debates, prompting criticism that he was chosen only because he's a safe pick. Despite his experience, he was quite reluctant. He apparently only agreed to host the opening debate after the format was set to six 15-minute segments. The first two minutes will be the candidates answering question, but each segment will mostly consist of "a deeper exploration of a topic," as the Times puts it. It's an intriguing variation, and I can see why it convinced Lehrer.
The odd part is why they bothered to court Lehrer at all and not go for Gwen Ifill. She works for the same program as Lehrer did — PBS NewsHour — so it wouldn't skew the network balance, and she's moderated two vice presidential debates. Even if the debates commission had its collective heart set on Crowley, I don't think anyone would have criticized them for having too many women. Having her would also mean that one person of color was moderating.
Interestingly, the choice of Crowley may have been spurred by a petition started by three 16-year-olds, as the Times reported in a second story. The petition eventually got 100,000 signatures, though the teens weren't able to deliver it to the commission.