Europe really does not like Xbox.
Having said that, they are very PC orientated so it's not overly surprising that Starfield did great but Xbox did not.
To be fair, when Xbox saw large parts of them as "tier 2" and not important as a focus with how they marketed certain things over the years it isn't an easy reputation to turn around no matter how long they've been trying to.
The way the reputation of MS and Xbox has been in Europe for years during multiple generations is exactly why I said that even when games start coming that are highly rated and seen as good, plenty of folks will just skip the game instead of buying an xbox to play it. There isn't a shortage of good games available on any platform so skipping some because they only launch on a platform you don't want to support or you feel isn't worth your time isn't a hard choice for plenty of folks with limited gaming time.