Modigent interview questions

I went through 4 interviews with this company, and received positive feedback after each one. On the 2nd to last interview, one interviewer wasn't able to make it into office and so I had to do a 2nd final interview, which they made sound like more of a formality than anything. Then they just stopped responding, at all. No "we've decided to go a different route", no feedback on whether they decided to move forward with another candidate or close the position temporarily. Nothing at all. 4 rounds of interviews, 4 rounds of interview prep + thank letters sent, anda lot of energy invested - the very least they could have done was provide some feedback or even confirmation that they weren't moving forward with my application. Very rude.