As others point out, nuclear bombs do not spontaneously go off. If they were that easy to accidentally trigger, building them would be no big deal and we wouldn't be talking about nuclear vs. non-nuclear countries to this day.

Furthermore, everything is space is already a weapon. The very act of being in space and not falling back to Earth means you are loaded up with enough kinetic energy to be going several miles per second. You don't need nuclear bombs to be a weapon in space, a bucket of sand is a deadly weapon. Militarization of space refers to things other than merely putting "big bombs" in space, where they are surprisingly useless. (Even the EMP is less useful than you'd think; space is already a sea of radiation so everything up there is already hardened against it.)