in reality all it took was one guy dedicating a couple of months of exclusive work to it This is wrong. Many professional mathematicians attacked the problem,

in reality all it took was one guy dedicating a couple of months of exclusive work to it This is wrong. Many professional mathematicians attacked the problem, and many useful discoveries were made before it was proved. For a brief summary, see https://en.wikipedia.org/wiki/Fermat%27s_Last_Theorem#Early_modern_breakthroughs https://en.wikipedia.org/wiki/Fermat%27s_Last_Theorem#Early_...