It is hard to get a nuclear weapon to detonate properly in the first place. Precise machining of intricate yet bulky parts, the most exotic timing mechanisms, shaped explosive lenses, corroding parts, half lives measured in days etc. They are almost so complex that if one minor thing goes wrong you end up with a conventional explosion and lots of contamination but very localized.
Sadly most people don't know this. They think a nuke will go full yield just by hitting it with a hammer.