If you're interested in movie soundtracks you ought to catch Edith bowman's podcast - soundtracking. She interviews directors and musical directors about their choices and process.

Also mark kermode has a show on scala radio where he plays his favourite soundtracks and scores from films.

They spent a tonne of money just getting the rights to it and then on the VFX, so it kind of makes sense they skimped a little on lesser known talent until they see how it goes down. I imagine if the acclaim grows and viewing figures support it there will be new additions further down the line with bigger draw.