Amazon Business Intelligence Engineer interview questions

I first had two rounds phone screen with Alexa team in Boston which went great. So I was invited to have an onsite interview with them. They arranged an one month later onsite interiew which I think was a little bit too late but out of politeness, I didn't push them. about one week before the onstie interview I was told the position was filled . Obviously, I was used as a back up. So the HR offered me another postion "analytics engineer" saying that they need one more round interview and if it goes well I can have my onsite interview. After the 3rd round phone screen ( I think i did pretty well, just behaviour questions ), there was no feedback so I wrote an email to push and the feedback was they need THE 4th round interview. I feel that I was used as a back up again and the process was too long for me to handle so I didn't follow up with them. Neither did they contact me anymore about THE 4th round interview. I hope they can work more professionally.