Ingvar Kamprad (the founder) is of German descent (his grandparents were german) so it is quite natural for him to expand to that market after Scandinavia, also being the largest economy of Europe doesn't hurt.

Germans like it cheap. And Ikea generally seems to offer a better quality than other cheap furniture chains. It's of course not only that germans prefer to pay less, but also that while germany is economically doing well a broad percentage of people had only little real wage increase in the last 10 to 15 years.

What surprised me more was that the Canary Islands was one of the first markets for IKEA (before 1985). I mean, the Canary Islands before Madrid or New York? WTF? I can only assume they were using as a test market, like Kansas City for Google Fiber, but still... wow!

Well there are a lot of swedish stuff in the Canry islands. It's probably the number one holiday spot for Swedes. Or at least it was back then. Just walking down the beach there you'll hear swedish everywhere. And there are plenty of swedes who owns a house there...

A lot of IKEAs early international expansion was franchisees, so it's probably more a question of someone there was interested in starting a franchise than that IKEA made a conscious decision that it was a market they were interested in.

No other big box brand ever gained signifacant market share in Germany besides IKEA. As competition is low, it's natural for IKEA to continue saturating the market. They are even building stores in city centers now, e.g. in Hamburg.

Also: Culturally speaking, Germans have (like the Dutch), always valued good product design. There's a nice cultural fit between IKEA (economical, good design) and the german market.