Might as well mean that they suspect the culprit, but they're not going to do anything anyway for this specific culprit, so let's all pretend it was an accident. Why make yourself look like a fool?

They already became a laughing stock once for promising the "strongest possible response" for the Nord Stream 2 sabotage [1].

[1] https://www.reuters.com/business/energy/eu-sees-sabotage-nor...