Typhlix
The MC doesn't remain stupid he starts to do things smarter in later chapters. The Author introduced the MC as an idiot muscle-brain who says he won't think because it hurts. The author later explains, in later chapters, that the MC really does feel real pain when trying to think about things. This is due to the fact that something changed in his new body when he transmigrated into this world and his brain works far to strongly for his cultivation level and his current body doesn't seem to be able to handle it. As we get into later chapters he starts to be less stupid and does things with a bit more thought. It seems to have gotten much better than the start of the LN. I've read up to chapter 307 so far.