Good question, so I went looking why:

David Andelman, in an oped @ CNN, thinks stupidity & incompetence, and I certainly buy that as a reason why they don't want to talk about it but get everybody interested in condolence calls instead. Fits the Trumpian model of a teeny State Dept. not communicating with an idiotic Homeland Security Dept. and a Pentagon that has to follow the President's Twitter feed to know what they are supposed to be doing:

What Chad has to do with Trump and Niger?

@ CNN, Oct. 21

[....] Chad's troops have for some time served as an effective ally in the region -- the best fighting force deployed in nearby Niger and Mali, with the best intel and best-trained warriors [....]

 

[....] And then Trump went and insulted them. In fact, the September 24 action was only the latest backhanded and ill-informed insult. It seems that US Homeland Security gave all countries 50 days to meet a "baseline" of security conditions, including producing a counterfeit-proof version of their passport to prove that they were reliable enough to allow their citizens into America. But Chad, desperately poor, had quite simply run out of passport paper.

They reportedly offered to provide a pre-existing sample of this type of passport. No dice. The next thing they knew they were on the banned list, alongside their arch enemy Libya and other clearly terrorist-driven nations.

Barely a week after the announcement of the new travel ban, the Chadian government suddenly began pulling hundreds of their fighters from Niger. There was no immediate explanation, though the nation's communications minister Madeleine Alingué condemned the Trump administration's unheralded move, observing that it "seriously undermines" the "good relations between the two countries, notably in the fight against terrorism." Hard to be more direct than that.

Troops from Niger and Mali were now all that now stood between the forces of ISIS and Boko Haram and our own military [.....]

Also explains to my mind the shell shocked look of McCain and Graham after being more fully briefed, Graham saying "we don't want to have another 9/11"