2. Because it's not clearly and entirely and immediately unlawful, and would take a court to rule about it (the courts are also fucked - SCOTUS recently ruled that lower courts are expected to defer to whatever batshit version of reality the government's lawyers are peddling) people in the chain of command can't clearly tell if the orders they are receiving are obviously illegal, and don't have good grounds to disobey them.
3. Also, that's, like, the way to civil war.
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[1] https://en.wikipedia.org/wiki/Little_Rock_Nine - When integration began on September 4, 1957, the Arkansas National Guard was called in to "preserve the peace". Originally at orders of the governor, they were meant to prevent the black students from entering due to claims that there was "imminent danger of tumult, riot and breach of peace" at the integration. However, President Eisenhower issued Executive Order 10730, which federalized the Arkansas National Guard and ordered them to support the integration on September 23 of that year, after which they protected the African American students.[4]
That's the more likely hedge. Their skin won't be in the fire in the case of the first one.