but you couldn't organise that in secret, could you? you would give the bank at least a few days of warning by starting the organising.
so either you not find not enough customers for your bank run - bank wins.
or you alert them in advance and they can take measures - bank wins.
Historicly, it was competing banks that organized runs on a bank that they suspected of cheating. They didn't need to tip off the bank in question, simply accumulate their banknotes and hit them hard with as many at once as possible while spreading a rumor that said competitor was insolvent. The term 'viral' was never used in this context, but that's exactly how we might describe such an event today. Once one was set off, the bank under attack wouldn't likely be able to take measures. If they could, then they were not insolvent, by definition.