California Hydronics Corp interview questions

After applying online, I was contacted for an initial interview with two members of the HR team. I was asked to take a mechanical aptitude test following that interview. I was contacted by HR again the following week to set up a second interview with the supervisor (upper level management) for this position. The interview lasted for nearly two hours and was followed by nearly another hour spent with a manager from another department. Both of them were extremely nice and I felt as if the interview went very well. They both indicated they expected to make a decision by the end of the week and the supervisor said I would hear from them either way. I followed up with a thank you email after the interview to both of them. I received no response from the supervisor, but I did get a nice reply from the other manager. Another week went by and I then contacted HR and was told they had offered the position to another candidate. I guess I expected that after a three hour long interview they would have contacted me to let me know they decided to go with another candidate. The fact that they "ghosted" me seems very unprofessional and surprises me given the way they all seemed when I met with them and the reputation of the company.