I guess they also don't want to blow up random civilians by accident again. When castle bravo was tested, we didn't knew that lithium7 fusion was possible and

I guess they also don't want to blow up random civilians by accident again. When castle bravo was tested, we didn't knew that lithium7 fusion was possible and that it would generate energy. The bomb had a lot of lithium7 because it was cheaper than lithium6. Castle Bravo then proceeded to explode with way more power than intended, it vaporized the measurement instruments, ruined the test site, damaged civilian property and caused a horrible amount of fallout that screwed a enormous amount of people from more than one country. Even during war, I suppose you want your explosions to behave in the way you expect... so you need to figure out all the physics related to them.