He was voted on by 14.5 million votes, which was 56% of the votes, but it is also out of a population of 45 million, and he only got 30% in the first round of votes. They have a completely different voting system to the US, so they had a second round of runoffs.
The point is, no most people in Argentina did not vote for him, but many did not vote at all.
Prices soar in Argentina after Milei’s currency devaluation (english.elpais.com)