You seem to be selectively ignoring my core point.
You're touting a narrative that distracts from the actual failure mode of these systems, repeatedly asking for the singular responsibility or legal culpability for the crisis, when that's not what I'm addressing.
My focus is instead on the systemic patterns that allow for these decisions to be made _without liability_. Of course no one person decided, "let's go out and screw over mortgage holders," there was simply no natural incentive to look too hard at if that was happening; and in a political situation wherein even basic protections can't be maintained, _of course_ there wouldn't be laws to assign personal liability.
It's funny that you bring up airline deregulation, as I consider that a wonderful example of exactly the pattern I'm citing. Although costs dropped, service quality followed alongside massive consolidation, soon accompanied by drops in employee pay and benefits, to the point that airlines now regularly file for bankruptcy and use that opportunity to further divest themselves of employee commitments while still giving massive bonuses to executives. (and similarly to the banks, in most of these cases _no one did anything illegal_)
Yet; there is still no hope of even re-instituting regulatory regimes, let alone punitive regimes. (look at recent airline behaviors in the news re: bumping and consumer abuses, and the extremely muted responses for examples of this. While that might not directly result from deregulation, it speaks towards an extremely un-empowered consumer base)
I would cap this rebuttal with a quote to directly shut down your assertion that deregulation has been "mostly positive", especially in light of your airline context, from the former CEO of American Airlines:
"The consequences of deregulation have been very adverse. Our airlines, once world leaders, are now laggards in every category, including fleet age, service quality and international reputation. Fewer and fewer flights are on time. Airport congestion has become a staple of late-night comedy shows. An even higher percentage of bags are lost or misplaced. Last-minute seats are harder and harder to find. Passenger complaints have skyrocketed. Airline service, by any standard, has become unacceptable."
To bring this ramble back to the point, I believe it's the wrong question to ask "what specific law did they break" when we've had a combination of conscious choice to trade worker and consumer protections for lower costs, and incentives aligned behind the powers that be to encourage that, such that even the most basic protections are non-existent, let alone a specific system of accountability.