During the financial crisis, the US government rescued the financial system from full-blown liquidation following Lehman’s collapse. The government rescued banks, bank holding companies, mortgage banks, securities firms, nonbank financial institutions, insurance companies, GSEs, and money market funds. All of this was done more or less on the fly, some of it within existing law, some on the edges, and some with new legislation such as TARP.
It is worth noting two things: (1) the government prevented a financial collapse; and (2) the total cost of the “Wall Street bailout” was zero. All of the Fed’s loans and most of the Treasury’s capital investments were repaid with interest, plus gains on warrants.
Following the successful resolution of the crisis, there was bipartisan criticism of the fact that the government “bailed out the reckless bankers”. You can still read in responsible publications that the Fed, the Treasury and the taxpayers spent “trillions” bailing out the banks. (If I lend you one thousand dollars overnight for one thousand days, I have supposedly lent you one million dollars.)
The legislative result of this populist outcry was the Dodd-Frank “Wall Street Reform and Consumer Protection Act of 2010”. The big debate over the bill was whether to end Too Big To Fail or allow it under special circumstances. The result was a fudge that sort of allows limited TBTF under certain circumstances for institutions deemed to be systemically important (dubbed "Sifis"). It reads to me as if creditors of failed institutions, such as bondholders of bank holding companies, are at risk.