During the financial crisis, the core issue is that banks were making loans off their own balance sheet with reserves too small to cover the losses that eventually occurred. In other words, when borrowers defaulted the bank itself lost money. This made them insolvent and caused the whole collapse.
In the case of Ant on the other hand, they essentially function as a lead generation platform for banks - currently 98% of "their loans" aren't really theirs at all, but rather are funded by their partner banks; if the loan defaults, it's the partner bank's problem, not Ant's.
The reason this change is such a big deal is that forcing Ant to fund 30% of its own loans will require raising an absolutely enormous amount of fairly expensive capital, driving up costs and significantly decreasing the value of the company.