They did not mix the audio correctly. So many people miss out on mixing and end up with all audio fighting to be heard. If you're not going to invest in a sound engineer to mix your audio, at least learn about using a simple compressor with side chain fed from the voice channel; it'll let people hear what you're trying to say even with loud music in the background.
I really appreciate this comment.... I always wondered why it's so hard to make music quiet behind voice tracks. But the words you used don't make any sense to me and they're not that easy to Google. I did poke around a bit though, and I think what you're talking about is referred to as "ducking"?
