Those investment banks weren't the reason for TARP now, were they? Banks like BofA, Citigroup, JP Morgan Chase were, and they all have investment banking arms. Nice try though.
TARP funds included entities like AIG that weren't commercial banks, and Bank of America took over Countrywide's assets, and JP Morgan Chase took over Bear-Stearns' assets when the market was already failing, much of TARP funds did end up dealing with those assets. TARP funds also went to auto companies. At any rate, the market would have been hit hard even with Glass-Steagall.