Irrespective of any subsequent arrests made, publicizing evidence of actual criminal activity is generally a social good, which often doesn’t (but can) overlap with vigilantism. Taking the term broadly, vigilantism is doing something that the law can’t/won’t do. Wikipedia discusses the various definitions, some of which require the use of force (something conventionally reserved to the law or government) but the broadest definition would include whistleblowing and community activism.

On the flip side, certain forms of publicizing evidence are illegal, such as leaking designated national secrets. In the USA, apart from that rather narrow exception, the First Amendment’s guarantee of free speech provides the legal cover to reveal the genuine evidence of someone’s criminal conduct, because criminal matters are: 1) in the public interest to expose, 2) an assailant cannot assert a privacy interest upon the evidence of their crime, and 3) the truth cannot be penalized by defamation claims. That basically covers any applicable USA free speech exceptions, although someone accused could file a frivolous lawsuit to financially harass the one who exposed the evidence. Such lawsuits are only punishable in the handful of states with anti-SLAPP laws, which is why more states and the feds need to adopt anti-SLAPP protections.

So from a legal perspective, leaking evidence of a crime is generally allowed. From a moral perspective, most would agree, and it’s why we have things like public trials. But does exposing crimes constitute vigilantism? I would say no, but others with a different definition might say yes, even if they agree that’s it’s legally and morally correct.