Many members of the political class believe that banking stability is one of the chief ends of public policy. How this monolithic belief came about, I'm not sure, but it's been operational for at least decades, as evidenced by the response to the 2008 financial crisis.

I suppose it may also be unfair to lay the blame solely at the feet of the policymakers. Members of the public would not be willing to accept the short term pain that banking failures would entail.