Unit4 Engineer interview questions

I applied online and received a call from the HR Rep within an hour to arrange a call for the following day for a screening interview. A couple of days later I received an email entitled "Next Steps with Unit4" informing me that the next stage was a video interview with the hiring manager and a member of the team and to book my slot. One slot was for in 24 hours time, the other in 48 hours time, both at 7am for me. It was short notice but I was glad things could be moving quickly. I confirmed the slot for in 48 hours to allow time to prep. A couple of hours later, I received an automated email from the HR rep's email address "HR REP would like to recall the message, "Next Steps with Unit4"." I thought it was unusual because I had replied to the email within an hour. Why recall an email hours after you've sent it and the recipient had replied? 24 hours pass since I accepted the interview time/date (at this point the interview would be in less than 24 hours time) and I still had not received call invite/link to confirm the meeting on their side. I emailed the HR Rep to check that everything was confirmed and still going ahead or not (I'm sure there was a mistake or they are just busy, right?) and that email goes completely ignored. Because it was getting close to the end of the day and I still had no reply, I called and left a voicemail too. I heard nothing back. Luckily I decided not to continue prepping and assumed it was not going ahead. The next morning and 45 mins before the scheduled time I get an email finally telling me they "apologize for the delay" and they have hired someone else. My point of this long review is not that I am annoyed I didn't get a chance at actually doing the interview I was invited to, although I'd have liked the opportunity to, but because instead of being courteous, professional and polite by telling me via normal human means of communication, such as a simple email, that for whatever reason in the 2 hours since I accepted the interview time/date that they no longer wanted to interview me, they weirdly tried to recall the interview invite without an explanation or follow up. I assume that they just wanted me to decipher the true meaning of this recall notification. Incredibly unprofessional.