There are kind of 3 types of loans:
- bonds. Loans interned to be bought by a range if investors and traded over time. Arranged and unwritten by investment banks.
- bank loans. The classic loan. The bank takes depositor money (that the depositor can take back anytime!) and loans it to someone or some company. The bank holds the loan
- private credit. Like a bank loan, but they get their money from long term investments by wealth people and institutions, add bank loans for leverage, and then hold the loan.
These are mostly syndicated. The traditional difference between loans and bonds was bank versus investment bank. The modern difference is in underwriting technique, degree of syndication/securitisation and loans mostly being floating and bonds mostly being fixed.
The Banks get in trouble, and Gov has to step in. So Gov, reasonably, add regulations and restrictions. But the law can't be really specific, it requires gov employees to actually examine the bank and make decisions (eg about risk levels, etc).
The banks have a really large incentive to chip away at the effectiveness of the regulation. They hire lots of lawyers, consultants, notable economists, etc and just keep pushing on these rank and file gov regulators. They buy influence with politicians, and use that to pressure the regulators. They hire some of the regulators at very high pay, sending a signal to the others: play ball and a nice job awaits you.
Over time, they just wear down the regulators. The rules are interpreted to be mostly ineffective and nonsensical. Often at that point the politicians come in and just de-regulate.
The banks just have the incentive and focus to keep at it every day for years. No one else with power is paying attention.