A number of reasons.

1 - in general, Argentines were sympathetic to Axis countries due to deep cultural and linguistic ties with Germany and especially Italy. In 1914, Argentina had ~8m people, ~30% of whom were immigrants. Of those, 43% were from Italy. Additionally, between 1921 and 1930, average 150,000 Germans emigrated to Argentina per year, joining a centuries-old population of Volga Germans in the rural provinces. Compounding on these ethnic ties, Argentina had a recent history of antisemitism: there were police-fomented pogroms in Buenos Aires 1919 and the Liga Patriótica Argentina attacked 'communist sympathizers', particularly Jews, during the great depression.

2 - technical expertise. Up to World War II, German scientists were generally acknowledged to be some of the best in the world, and Argentina sought to attract them to build and improve the national educational establishment. Similar desires motivated American and Soviet agents to recruit former Nazi scientists after the war via Operation Paperclip.

3 - nation building. In 1946, the Peron government was showing fascistic leanings - Peron himself was a personal admirer of Mussolini. Person offered former Nazis and collaborationists explicit protection. Some of them went on to prominent positions in the Argentine government.

4 - money. Nazi officials looted tremendous amounts of European art and treasure. This helped ease their escape and make them attractive to other countries.

5 - anti-communism. Peron wanted to position Argentina to take full advantage of the cold war through nonalignment, and saw former Nazi officials as trustworthy anticommunists.

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