To summarise, because Rachel Maddow takes forever to make a point:
Chad is the most potent military fighting force against Islamic extremism in the Saharan African region.
Chad is one of the USA's key fighting allies in the region. Wherever Chad sends troops, Boku and ISIS get pounded out.
Chad was in a wrangle with (Rex Tillerson's) Exxon over billions of unpaid tax. That was resolved in June.
At the end of September the (Tillerson's) US State Department put Chad on Trump's travel ban list.
At the end of September, Chad began pulling it's armed forces out of the likes of Nigeria, Niger and Mali.
A few days after that, four Americans get ambushed by Islamic extremists in Niger.
Trump says nothing for two weeks.
https://www.youtube.com/v/rAJ7_U5ZILIOr Chad may have ended up on the list because they were late getting the sample passports to the US that the latter had demanded. They had a stationary shortage.