[This previous answer] (https://old.reddit.com/r/AskHistorians/comments/4vz0ad/asianamerican_what_led_to_the_large_japanese/) from /u/yignko goes into economic details that led to Fujimori's rise. Many credit Fujimori and Cambio 90's successful recruitment of business leaders from the informal sector, plus small and medium sized businesses.

In addition to the points made in that answer, I wish to add a few points.

Fujimori's rise was not without racial prejudice. In the same way that we remember the Birtherism issue with Barack Obama, Fujimori was attacked by opponents as someone not born in Peru but in Japan - something that would disqualify him from office.

Throughout the campaign in 1990, voters said things like “A Japanese can’t govern Peru. A pure Peruvian, native to here, has to assume the presidency.”

But these facets of Fujimori played to his advantage in contrasting him with the leading opponent, right-wing Mario Vargas Llosa. Llosa, in his way, represented the Peruvian political establishment and also white or European Peruvians.

During the 1980's, Peruvians lived during what was called "Manchay Tiempo" - a time of fear. Shining Path, a far-left Marxist-Leninist-Maoist guerrilla force led by Abimael Guzman terrorized Peru with intense, violent, and authoritarian action in the Peruvian highlands. Shining Path's actions, such as the massacre of eight journalists in Uchuraccay, led to Peruvians leaving the country for abroad as well as internal displacement of mostly Indigenous Peruvians - "dezplazados."

These dezplazados overwhelmed social assistance networks and many failed to receive aid. During the Dirty War, many Peruvians felt they lacked a side - either Shining Path who killed indiscriminately; or the government whose soldiers fought a dirty war that included cases of rape like Raquel Martin de Mejia. So you can imagine a cynicism against the government. Even for Vargas Llosa, prestigious as he was, couldn't alleviate that cynicism. When he visited the highlands for a report on Uchuraccay, he visited with an anthropologist and treated Indigenous Peruvians as if they were exotics - performing rituals like tinkay out of context - and referring to them in a report as "ancient, archaic."

One group that did help dezplazados and the poor: Protestants. Protestants have existed in the margins of Peru since the early 19th century, but during the 1980's they successfully began to convert more Peruvians to Baptist, Presbyterian, and Pentecostal faiths. "One in ten Peruvians ]converted] to Pentecostal Christianity during and after the dirty war." Protestant groups such as Peruvian Evangelical Church (IEP) had several thousand congregations in the Andean highlands and Protestant churches made inroads in shantytowns that emerged in Lima. Protestants felt in a "crossfire,” as Pastor Luis Minaya Ballon put it, between the Catholic majority and the Shining Path who killed many of their parishioners and pastors.

The time in 1990 felt ripe for an outsider. Alberto Fujimori played into his outsider status through an alignment with the political party Cambio 90 or "Change 90." While businesses form the small and medium sectors played a role in Cambio 90, the Cambio 90 also drew support from a seemingly marginal Protestant group who actively recruited members.

Fujimori also "campaigned wearing traditional indigenous clothing and hats, symbolically making the point that Peru’s indigenous and mestizo voters" could see him as aligned with their issues (Kushner, 2007). Despite being born to Japanese Buddhist immigrants, Fujimori converted to Catholicism. He used his life story to straddle Peruvian stereotypes of Japanese as hard working and efficient - "Honesty, Technology, Work" was his campaign slogan. He called himself El Chino - "The Chinaman" - a term used by Peruvians to refer to anyone who is East Asian. Fujimori had no political experience - he held a rectorship with a university. But he did host a TV show on Peruvian TV.

Fujimori bridged his outsider status - a "Japanese Peruvian" - with his connections with Peruvian culture. But Japanese Peruvians - Nikkei - felt ambivalent if not weary about him.

Japanese immigrants began coming to Peru in the mid-19th century working in mining and, alongside Chinese laborers, to dig guano ("The Age of Guano"). Japanese immigrants created new businesses, with tanomoshi - "pooled money in cooperative arrangements" (Kushner, 2007) lent to families to created businesses.

Nativists resisted Nikkei businesses, which resulted in riots like the Lima Riots in May 1940, and compliance with U.S. pressure to intern Japanese-Peruvians in places like Texas. Because of this and because of their low demography, many Peruvians preferred to avoid an activist political stance. “The whole colony is afraid that he’ll do a bad job and that 91 years after our grandparents arrived, he’ll fail, erasing the positive image that the colony has worked to achieve” (Kushner, 2007). Many Nikkei preferred Vargas Llosa and his platform, and many did not come out to support Fujimori worried that his failures in policies or governance would result in a nativist reaction or backlash. Fujimori's Japanese Peruvian wife Susana Higuchi criticized these Nikkei, saying “The nikkei are passive. There are few nikkei who fight..."

When Fujimori won, Peruvians reacted with split feelings on Nikkei: both a Japanophilia, but also with racist attacks such as the murder of Japanese tourists in 1991.

But, Fujimori's success led to "dekasegi," a "reverse migration" (Kushner, 2007) which many Japanese Peruvians who left returned to Peru.

Sources:

Kushner, E. (2007, September 25). "Japanese-Peruvians-Reviled and Respected: The Paradoxial Place of Peru's Nikkei." NACLA. https://nacla.org/article/japanese-peruvians-reviled-and-respected-paradoxial-place-peru%27s-nikkei

Starn, Degregori, & Kirk (Eds.). (2005). The Peru Reader. Duke University Press.

"Change '90." http://countrystudies.us/peru/83.htm

Nolan, R. (2019, July). "A Jagged Scrap of History." Harper's Magazine. https://harpers.org/archive/2019/07/a-jagged-scrap-of-history-shining-path-peru/