Because during bad times the ones that make bad decisions don’t survive or at very least are removed from positions of power.
The ones best equipped to get in positions of power during “bad times” are bad people willing to put their ambitions above basic human decency.
It’s not actually clear that it only affects huge companies. Much of open source AI today is done by working with models that have been released for free by large companies, and the concern was that the requirements in the bill would deter them from continuing to do this. Especially the “kill switch” requirement made it seem like the people behind the bill were either oblivious to this state of affairs or intentionally wanting to force companies to stop releasing the model weights and only offer centralized services like what OpenAI is doing.