There's a little detail about arresting the right people that you don't care about, and there's a little detail about the fact that no crime was actually being committed that you don't care about.
That is an embarrassment to this forum, but I don't ever expect you to recognize that.
If anyone had actually been arrested for offenses that instigated the past complaints, you might have a point.
But, no one was arrested for those offenses. Instead, everyone were arrested for an offense that was unsubstantiated. As a result, even those that may actually have been committing another offense walked away. And now the city is even offering to foot the bill for expunging those arrests.
Police cannot arrest someone for an offense that wasn't committed today because one may have been committed in the past. So no, the past isn't relevant in this case.