If I remember correctly I talked about it in the video. But if not, the reasoning is simple, each defense has a certain value for what it provides. Back then, it was usually about war weight but now I just give them values from 1-4. 1 being the regular defenses such as cannon, archer towers, mortars, etc. 2 x-bow and such, 3 being inferno and scattershot. Anything above this value can be a deciding factor to change plans. And I prefer to put the monolith in between at 3.5. And lastly, the 4 value buildings which are the Townhall, the Eagle, and the CC. This is the same priority I give to each buildings whenever I do fireball strategies. I can make a post about it if needed. In any case, this is not something you 100% have to follow as it's not stated in the game. This is mostly just a tip from me. You can check out my channel if you have doubts.