The will of the plurality you mean? He didn’t win a majority of the votes. He is the legitimately elected office holder; but it was not the will of the people, it was the outcome of this particularly electoral process. Many American electoral processes require a run off without a majority for this reason, and it’s an intensely weak platform to claim a mandate from - not only did more people not vote for you than half the voters, if you add in the people who could vote but didn’t, it’s by far not “the will of the people”.