Why couldn’t they use a grand jury in Kansas?
They can use a grand jury in any federal district where the offense took place. And probably some of her use of her private email may have been in Kansas. BUT, remember, the DOJ doesn't want to indict. They won't be forum shopping for a GJ that will indict. They are happy to go before a DC grand jury and get a "No Bill" and then report that the grand jury found there was no evidence of wrongdoing. Hill and the DOJ are off the hook.