If donating money to politicians didn’t buy influence companies wouldn’t do it.
Quote from elizabethwarren.com:
I will break the NRA’s stranglehold on Congress by passing sweeping anti-corruption legislation and eliminating the filibuster so that our nation can no longer be held hostage by a small group of well-financed extremists
That isn't limited to guns or because of the gun lobby. It's because moderate Republicans might as well be Democrats.
The price of having a politician on your side (ie lax financial regulation) is lower if he already believes in lax regulations.