ESO on XB1 also has no competition in the form of FFXIV Online, which is proving to be doing pretty well on PS4.
Your opinion seems a bit baseless and is a big stretch. There are plenty of MP focused games that have sold more on PS4.
It does have competition, Neverwinter is on X1. Of course FFIV is a much better game so after all these comments I tend to agree with you all on why ESO sold more on Xbox. It wasn't something I considered originally.