This is the problem, you again apply a broad brush without understanding the implications.
Rail bonds were held by wealthy, and pensions, as a primary holding like any other corporate bond, whether high yield or investment grade. You are blaming Securitization for something it wasn't even involved in.
That only rbms blew up is a testament to the fact that overall abs, including most CMBS and Clos were structured well and rated appropriately. The difference with rbms was in the assumptions around home price appreciation (hpa) being poorly understood (they couldn't go down), loss estimates on old products being offered to new borrowers (no/low doc and option arms used to be specialty products for appropriate borrowers but nobody shifted loss expectations appropriately when they went down credit) and correlation, as well as near 100% leverage through selling down everything, including the equity. Hence the new risk retention rules requiring some skin in the game.
The crisis was not Securitizations fault, it was a combination of factors that included it.
Making excuses. Home prices have declined previously, well within memory of anybody over the age of 40. They fell precipitously in many areas as part of the S&L crisis. If you think that highly successful veterans of decades of working in finance didn't know that, you're delusional. They just kept pushing the limits to make more money, knowingly lending to people who couldn't pay & representing that as good debt in a hot market where too much money was chasing too few returns. The smartest among them paid for protection in the synthetic derivatives market above and beyond any risk they had.
They knew it would all fall down, although few realized just how bad the collateral damage would be. They're like cowboys who'll ride a horse to death.
Like the stock market, housing prices thrive on illusions & are therefore subject to the attentions of hucksters & pitch men.
In all of this, you're deliberately avoiding statements & actions by both sides of the political divide as to what they want. Dems say we need to go further wrt oversight & regulation, Repubs try to roll it all back to the good o' days of the Bush years & even further if possible.
They suck voters in with emotional bullshit- you over immigration, others over abortion, taxes, guns, smaller gubmint & an ongoing 3 ring circus of contrived scandal.
Repubs serve the predatory financial elite almost exclusively. Once a person realizes that all other arguments fall away as peripheral no matter how badly they want to convince us otherwise.