You make a good argument Nulle.
All I can say is that it is probably not easy for these Russian speakers to simply emigrate to Russia even if the thought occurred to them. Perhaps all their family and friends are in Latvia, they were born and grew up there. Plus it is expensive to emigrate. The immigrants to Sweden have no ties whatsoever and no group is very large. None of the individual groups are over 1% of the population with the exception of Finns. Also there is absolutely no shared history.

However, an interpreter is provided to them for free for quite a lot of different circumstances, such as police and hospital etc if they can't communicate in Swedish. My view is that this is excessive and too expensive to be tax subsidized. It's political correctness going too far in the other direction! A

Sweden historically give gives out state information in Finnish and Sami in some areas though - but I don't come from such an area so I don't know how it works. There is practically nobody in that group who can't speak Swedish.

Yes, the ferry was Tallink. In contrast, getting off the ferry there were lots of information in Russian, including "Welcome to Stockholm", maps, tour guiding etc.