That one is on the regulatory agencies as well - they looked on silently as larger banks gobbled up smaller ones, or in the case of UBS/CS, actually forced them to merge.
"Too big to fail" means the regulators tell you what to do /all the time/, not just after you've failed.
You don't want to be too big to fail! There's a lot of businesses only small banks can do, like backing sweep accounts and neobanks like Simple/Aspiration.