Puchacz belive it or not but in ancient times bilingualism wasnt rare at all. Ancient Rus were mostly traders so they had to know some form of Slavic language. You had to know local Slavic language if you wanted to trade. How do you think people all over Europe traded between each other, surley they didnt spoke Latin, they spoke a language of those with whom they traded goods.
Religion wasnt problem back then, people always accepted foregin god's. Romans prayed to their and foregin god's and so did other people. Rurik wasnt Swedish nor Norwegian. Swedes were just one of many Scandinavian tribes back then. Rurik belonged to a tribe of Rus so he cant be Swedish neither Nrowegian.
"Why would Slavs ask a non-Slavic ruler to come?";
And why wouldnt they? Polish-Lithuanian commonwealth had many non-native, non-slavic rulers like example, Habsburgs, Anjou's, Bathory, Valois and so on and on. What about House of Luxemburg which ruled slavic speaking: Bohemia (Czechia), Moravia, Silesia and both Lusatia's? House of Luxemburg is of germanic origin you know. Not to mention Russia's House of Romanov. Romanov's full name was House of Holstein-Gottorp-Romanov. According to you i should wonder why did Romanov's marry a non-slav?
In early medieval and late medieval ages and later, there were many non-native rulers and nobles. Infact majority of rulers wasnt native. Nationality wasnt a problem for people.