To be "credible", a guarantee must be structured so as to burn a large enough share of the bank's creditor, so that the good assets in the overtaken bank eventually pay for the takeover.

Typically, bond holders should be burned, because they are smart investors who should know better than pour their money into a shit pile (tm).

Retail depositors and SMB are financially uneducated (relatively speaking), and checking accounts are a necessity of a functional daily life. Therefore they should be protected.

The only remaining question is that of the per-account cap on the guarantee. A lower cap adds to the credibility that the guarantee will work for what little is has promised. But it has been noted that many SMB should benefit of much larger caps than 100k€/$ to meet payroll obligations without anxiety.

Pierre