A real two-year old's understanding of finance and markets shown here.

manipulate the investments and stock markets to "whoops, just became valueless Monopoly money, let us take it off your hands"

This has never happened - no bank has ever seized investments during a market crash. Are you mixing it up with how FDR seized gold?

Aside from that, the last market crashes were not caused by manipulation, they were caused by an error in how risk was calculated in their systems. In 2008, debt books based on mortgage repayments were regarded as low risk because their trade value didn't fluctuate. This meant that every institution was heavily exposed to them because "zero risk" and decent reward. When those mortgages started defaulting because they were actually a high risk default despite what the systems said, those institutions largely collapsed. Lehman Brothers were the largest casualty and Citigroup arguably should have joined them, but instead was bailed out with the Big 3 automakers and other mismanaged businesses that were destroyed in the resulting collapse.

2000's market crash was caused by overspeculation on assets based off future value, think if the whole market was made up of hype stock like GME, RIVN and PLTR. This was largely the work of retail traders enamoured with the possibilities the Internet brought.

A real two-year old's understanding of finance and markets shown here.

manipulate the investments and stock markets to "whoops, just became valueless Monopoly money, let us take it off your hands"

This has never happened - no bank has ever seized investments during a market crash. Are you mixing it up with how FDR seized gold?

Aside from that, the last market crashes were not caused by manipulation, they were caused by an error in how risk was calculated in their systems. In 2008, debt books based on mortgage repayments were regarded as low risk because their trade value didn't fluctuate. This meant that every institution was heavily exposed to them because "zero risk" and decent reward. When those mortgages started defaulting because they were actually a high risk default despite what the systems said, those institutions largely collapsed. Lehman Brothers were the largest casualty and Citigroup arguably should have joined them, but instead was bailed out with the Big 3 automakers and other mismanaged businesses that were destroyed in the resulting collapse.

2000's market crash was caused by overspeculation on assets based off future value, think if the whole market was made up of hype stock like GME, RIVN and PLTR.