There were a lot more details. You left out the PMIC insurance policies.
One of the basic ideas was that any home loan that defaulted was that 80% of the sales price would be recovered in a bankruptcy. So borrowers with less than 20% down were required to buy an insurance policy covering that 20%. This worked all well and fine until the housing bubble burst and the bankruptcy recovery and mortgage insurance didn’t cover the actual loss. Then the bonds began to fail, margin calls caused the markets to fall . . . it’s too late for the pebbles to vote once the avalanche has begun.