Complex sentence: Seibu Kaihatsu changed the name to "Raiden Fighters" before its release, due to the fact that people paid more attention to it during market tests just by the simple fact that the game had the word Raiden in its name.
Split into simpler sentences: Seibu Kaihatsu changed the name to "Raiden Fighters" before its release. In pre-release market tests, Seibu Kaihatsu discovered that people paid more attention to the game when it had the word Raiden in its name.