ClimateWorks Foundation Program Manager interview questions

There were 3 rounds of interviews (first with HR, second with a panel of staff who are not directly in the team, last one with the team members and hiring manager). I also had to do a 3h exercise before the last interview, which was relatively easy and a direct application of what the job would focus on. Everything was remote. It was a good experience until they GHOSTED me! The staff at the last interview also seemed a bit distracted, which did not give me a great impression. The first 2 interviews were very professional and staff was friendly and engaged. After all the time invested in the process, it was extremely disappointing to not even get an email from HR indicating that I did not get the job (I followed up multiple times with HR and 2+ months after the last interview I haven't heard anything). How long does that take to write such an email? Two minutes? Don't ask candidates to go through 3 rounds of interviews and 3-hour long exercises if you are unable to notify them of the results of the process.