I don't think there's "an" explanation. There are lots of false reviews on the internet. Some are honest mistakes, like you said. Some are intended to artificially raise or lower the target's reputation.
And some are stolen, automated, or low-effort content that's not intended to affect the target at all, but exists only to make the account seem legitimate so it can't be trivially identified as having the sole purpose to astroturf one target.
I think there's plenty of reason to believe each of these categories is responsible for a ton of internet content.
And some are stolen, automated, or low-effort content that's not intended to affect the target at all, but exists only to make the account seem legitimate so it can't be trivially identified as having the sole purpose to astroturf one target.
I think there's plenty of reason to believe each of these categories is responsible for a ton of internet content.