That page is getting weird - I am in the UK, but being fed a Japanese language page for no logical reason.
( マンマ・ミーア - Wikipedia )
For me, in GB, the Wikidata page is the single with no links to any languages. The Wikipedia link goes to a GB disambiguation page. So I can’t work out why MB is showing me a Japanese disambig page?
This does seem to be an example of the song\single mess that is happening at Wikidata. On the Wikidata page they have removed all the links to the Wikipedia SONG(work) page as this is a Wikidata SINGLE page. They don’t like it when a Wikipedia page shows both Song and Single data on the same page.
That does not explain why the Wikipedia link is failing so badly for MB. I would have hoped it at least would load up English - instead we get a random language. Very odd.
Edit - for that MB Single page, the wikipedia link should go to https://en.wikipedia.org/wiki/Mamma_Mia_(ABBA_song) and not https://en.wikipedia.org/wiki/Mamma_Mia_(song) as it currently does (I have now added an edit to swap this - but that is only a UK solution. No Wikidata link available to point to multilingual Single pages)
(Edit Update: This has been approved so you’ll have to take my word for it that I was seeing Japanese as the approval has therefore masked the bug caused by the redirect)
If the Wikidata link went to https://www.wikidata.org/wiki/Q1131308 MB would again load all the languages. But as that is a SONG page the Wikidata editor would just return and delete the link from MB and restore it to https://www.wikidata.org/wiki/Q109427725 Wikidata needs to solve their puzzle with Wikipedia over this and find a solution. Song and Single need to point to the same combined Wikipedia pages.
For now the only real answer for MusicBrainz is adding all the different language Wikipedia pages separately! Maybe MB can come up with a hack to get round this. You can’t even do it with a look-up on Wikidata as there is no link between SONG and SINGLE pages. (which seems weird)