Carrier Product Manager interview questions

Contacted by a recruiter, set up with a phone call with the hiring manager. Recruiter did initial screening and then the hiring manager called at a later date. Hiring manager was professional and well spoken.

I was contacted by a recruiter. I had one initial phone interview with an HR manager. Then I had two phone interviews with the hiring manager and then the general manager of that group. They brought me in for an on-site interview on a Friday about 2 weeks after the last phone interview. It was with 5 different people. Everything went well it seemed. They said they would get everyone's feedback and get back to me the following week or the week after. Two weeks go by without any feedback. I called the recruiter and he told me that they said that they didn't have everyone's feedback. The 3rd week was a convention that everyone would need to go to, so I would probably hear back about the next steps during the week after which would be the 4th week. On the Friday of the 4th week, exactly 28 days after the interview, the recruiter emails me saying that they have decided to go ahead with another candidate. So, I have no problems at all with them hiring another candidate of course, because that's their right. But considering they didn't have everyone's feedback for me for an entire month, how did they get another candidate all of a sudden? The professional thing to do would have been to just be straightforward with me and tell me that there are other candidates in play. In that case, no harm done. I was expecting some professional courtesy from a big corporation like this, but apparently I expected too much.