It was initially reported the way it was because that's the extent of the video that was first available. The reports were corrected fairly quickly and at this point you'll find significantly greater information presented about the incident. There is no indication at all that major news outlets intentionally withheld information or promoted a story that they knew to be false.
There has been no retraction. There was never a need for one. CNN has several stories on their front page that dig deeper into the incident. They aren't hiding from the truth at all.
https://www.cnn.com/2019/01/22/opinions/washington-dc-marches-national-divisions-maltby/index.html
https://www.cnn.com/2019/01/21/tech/twitter-suspends-account-native-american-maga-teens/index.html
https://www.cnn.com/2019/01/21/us/maga-hat-teens-native-american-second-video/index.html
So this is not a case of burying the retraction. This is a case of intentionally misleading video being spread across the internet and then reported on by major news outlets. Nathan Phillips was interviewed, and had he been honest this would have been cleared up very quickly, but he fed into the false impression the first video presented. More information came out (the news media is not all knowing, if you can show me that they had proof that their reports were false at the time they aired them then show that) and none of the major news outlets hid from the truth.
I agree with you that Nathan Phillips should be considered a non-credible person. I'd even agree that he was likely intentionally dishonest and misleading. What were his motivations? I don't know for sure. But of the three groups in this incident I think those kids share the least amount of blame. Both the Hebrew Israelites and Nathan Phillips were the primary instigators, and that's a conclusion you'd likely come to if your one and only source of news was CNN.
Just a small aside, and a real question that I don't know the answer to. You mention Nathan Phillips film crew? My assumption is that this is video shot from a phone camera. Is there some source indicating that Nathan Phillips had a film crew?