Suppose we agree. In fact, I think I can agree with that...
Why is it $40 billion a year? I'm not a Musk fan per say but it is the closest analog... you can buy almost 2 SpaceX's (the entire company) a year for that and I highly doubt modernizing the nuclear infrastructure is that much more complicated than R&D on a brand new space company.
Some of us don't necessarily disagree we need to spend money on defense. But we think the amount being spent is way more than should be reasonably necessary to get the job done.
People like to criticize people who want to cut military budgets never asking if maybe we should just fire a bunch of people at the top who are inflating all the costs and replace them with people incentivized to get us more for less money.