Explanation as to why Tobi used to be childlike and weird? Tsunade Orders to Capture Itachi And Akat

Explanation as to why Tobi used to be childlike and weird? Tsunade Orders to Capture Itachi,
Tobi vs Naruto, Kiba, Shino
Sakura, Sai, Kiba and Rock Lee vs. MS Sasuke
Tobi VS Naruto, Sakura, Shino, Kiba, Hinata, Kakashi, Yamato, Sai
Tsunade Orders to Capture Itachi and All Akatsuki - Obito vs. 8 Man Squad

Explanation as to why Tobi used to be childlike and weird? Tsunade Orders to Capture Itachi,Tobi vs Naruto,Kiba,Shino,Sakura,Sai,Kiba and Rock Lee vs. MS Sasuke,Tobi VS Naruto,Hinata,Kakashi,Yamato,