The Western fascination with Japanese culture never really died, although certainly became unfashionable around World War II. My reading has mostly dealt with the artistic exchanges between Japan and the West so that is where most of my knowledge is from, maybe someone else can discuss how economic changes in Japan post-WWII affected the West's perception of Japan.

The dissemination of Japanese art and printmaking after the opening of Japan in the 1850s coincided with both the increasing use of printed advertisements, on which ukiyo-e art styles were a big influence, and impressionism. Both mainstream impressionists and the more flamboyant incorporated Japanese media into their art, whether in the form of aesthetic influence (as did Van Gogh) or by painting scenes that included Japanese art or textiles (Whistler). The presence of young Japanese men in Paris, who were sent to learn Western ways and report back to the government on life outside of Japan, were a source of huge fascination to Parisians at the turn of the century; in the other direction, the writer Lafcadio Hearn also acted as a sort of ambassador between Japan and the West, living out the end of his life in Japan and writing essays about life during the Meiji period. Collecting Japanese art, because of its relative rarity and expense, was a huge trend among wealthy art collectors during the Gilded Age. Mainstream interest in Japan really picked up after the Exposition Universelle in Paris in 1900, where visitors could see pagodas, textiles, and so on. But trends ebb and flow, and to Westerners the Japanese aesthetic was certainly no exception.

I can't speak directly to the presence of Japanese aesthetics in the West in the 1920s, but the end of the Taisho period and the rise of militarism and an anti-modern, anti-Western sentiment in the 1930s was the source of a lot of Japanese resistance to Western cultural interactions. Eri Hotta briefly covers the fashion of wealthy young Japanese men receiving their educations at Oxbridge or (more typically) Ivy League universities, and returning home confident in the superiority of Japanese morality and intellectual thinking. The heavy policing of both pro-Western sentiment and the suspicion placed upon those importing Western goods certainly didn't promote an air of cross-cultural exchange, either; like I say, my interest is in art rather than economics so I can't say how the Great Depression may have measured into a slowing of importing Eastern goods.

In the postwar period, once again, artists led the resurgence of interest in Japanese art forms, this time with the beats and haiku (Kerouac especially was a prolific writer of English haiku). Relative to the earlier Japanese trend this was a minor rise, but is still relevant, I think. The art of Japanese filmmaking also began to get international attention with Akira Kurosawa, who won the Venice Film Festival in 1950 and was a huge influence on arthouse filmmakers of the 50s and 60s, including Federico Fellini and Ingmar Bergman. (These filmmakers' subsequent influence on the New Hollywood wave including George Lucas, Francis Ford Coppola, Steven Spielberg, etc. transmitted the influence of Kurosawa down the line, so to speak.) As to the period of the 1970s and beyond, Susan J. Napier writes that the rise of Japanese fandom in the West is largely attributable to interested university students who organized clubs beginning in the late 1970s and dramatically rising in the 1980s, with the spread of VHS videotapes.

I believe the main differences between turn of the century interest in Japanese aesthetics and modern-day fandom are these, and I base these on Napier and Koichi Iwabuchi's Recentering Globalization (which deals mostly with the spread of Japanese pop culture in Asia, but is a very interesting introduction to the contemporary international circulation of media and culture):

• the historical interest in Japanese aesthetics tended to be centered on particular art forms and existed within elite circles, either wealthy, artistic, or both, and thus wasn't truly mainstream beyond a generalized trend (as I mentioned in reference to the Exposition Universelle);

• the ease with which Westerners in the modern age can access foreign cultures (i.e. how cheap and easy it is to get everything from anime to translated literature to actually traveling to Japan);

• the theory that globalization eradicates a sense of inherited cultural identity in individuals who then pursue what they perceive to be more cohesive cultural identities, which I think gets to the heart of what you're describing as "weeaboos"

Sources: Susan J. Napier's From Impressionism to Anime: Japan as Fantasy and Fan Cult in the Mind of the West (2007) (my main source and very highly recommended for further reading in this area); Lionel Lambourne's Japonisme: Cultural Crossings Between Japan and the West (2007) (not an academic book, but exhaustively researched), Eri Hotta's Japan 1941 (2013); Koichi Iwabuchi's Recentering Globalization (2002).