I really don't like offering opinions on questions, but you've asked politely and clearly, and I want to oblige you. Please note that no disrespect is intended; I'm analyzing potential reasons for downvotes, not judging you as a person. Most of the following are what I call "fellow traveller" reasons - whether or not you intended the implication, these concepts are common among weak questions, and the association leads to downvotes. (In my neighborhood of the country, it is perfectly possible to be a nice person wearing a tie, if you wear a tie everyone will assume you are a complete waste of oxygen.)
This is written as a "I think x amiright" (quoting from [help]); it is advancing an alternate theory of history. It is possible that if you were explicit about that you might avoid some downvotes.
the phrase "I find it very hard to imagine" is, in my experience, associated with low quality questions. Imagination indicates that you're advancing an alternate theory of history, but it is strongly associated with questions where the author wants to substitute "imagine" for "research".
You're asking two different questions - (a) Was Japan interested in the Japanese population? and (b) Are all prior historians wrong in assuming Japan attacked Hawaii for strategic reasons. I don't think either question is as strong as directly asking "Which analysis of Japan's motivation is more strongly supported by evidence?" - a question that can be researched.
The question confuses propaganda with reality. Germany claimed to attack the Sudentenland to protect the Germany speaking population, but I think it is pretty clear that their objectives were world domination and genocide from the start. This leads the question to privilege the racial purity argument and to undercut the plausibility of the strategic objective. This makes it difficult to engage with the question directly & honestly.
You're asking about Japan, but using Germany's actions to support your analysis; that's questionable at best. Japan and Germany were (at least to my reading) more partners of convenience than ideology. I think I've read something recently about internal German commentary on their view of the value of the Japanese alliance (which was pretty low).
Because I hate the feeling of providing only negative commentary, I'll provide my back of the envelope suggestions to improve the question.
- Omit all mention of Germany, unless you can show some relationship between the motivations of the two countries.
- Explicitly address why you are discarding all prior published analysis.
- Explicitly state that you're examining two alternative theories of Japanese motivations.
- show any research that you've done that would indicate that Japan was motivated by concerns for the Japanese population of Hawaii. Were the Japanese in danger? Was this strategic expansion (that kind of muddies the line between the two)