If the Defense Department is diverting billions for Trump’s wall, does the Pentagon really need all that it's getting?

The Pentagon is diverting 3.6 billion dollars of its budget to help build Trump’s wall. Shouldn’t people be asking the obvious?: Does the Pentagon really need all of the $686 billion it got this year for military spending? Shouldn’t the issue of military spending be in the front and center of the 2020 presidential debate? 

https://www.aljazeera.com/news/2019/09/pentagon-oks-military-construction-funds-build-trump-wall-190903222002335.html