To be fair, HAARP is a big unknown. The official record is that it was used to research the ionosphere. I had previously heard that the ultimate goal was to leverage the hypothesized discoveries into advanced communications capabilities, but I don't know if that was ever an official statement or not. One supposed goal was to build a new way to communicate with submarines at depth. There was only ever one array built and it was in Alaska in a forest, not on a sea-based rig. It was shut down a few years ago citing funding as the cause.
Whether or not it created any actionable scientific discoveries or not, or if the Alaska array was shut down for other reasons will likely never be known by most of us. I suspect the research outcomes will remain classified for many decades to come, even if the results were "we didn't find anything new."
HAARP is a conspiracy-theory goldmine because it's shrouded in both government secrecy and difficult-to-understand advanced science. It breeds a wealth of theories of its capabilities ranging from weather control, earthquake creation, inducing mass hysteria, etc. Like most things of this nature, you'll never convince some folks that it's true, and you'll never convince other folks it's not true.