I guess you're right that food is historically speaking extremely safe. I guess with this specifically, the issue is about how connected one company can be to the whole food supply.

A farmers market stand may not have perfect food safety either, but their outbreak would be limited to the few people who bought something on the farmers market (or maybe a cafe/restaurant or two that they supply).

Most likely, any harm wouldn't even be traced back to any individual salad because the sample wouldn't be big enough to form a pattern people would notice.

But because they supply so many salads to everywhere, it's a major issue that affects the whole food system.

I guess it's similar to an AWS outage. Companies constantly have outages, but an AWS one takes down half the internet.