Complex sentence: Infamous Metropolis mob boss Bruno Mannheim offered to bankroll Schott to build the toy factory, but unbeknownst to Schott, Mannheim used it as a front for a numbers racket.
Split into simpler sentences: Infamous Metropolis mob boss Bruno Mannheim offered to bankroll Schott to build the toy factory. Unbeknownst to Schott, Mannheim used it as a front for a numbers racket.