His early abdication is his answer to the massive trolley problem he was facing: hold fast to Numenor’s traditions and ways, but run the risk of giving away Middle-Earth to Sauron and have him go after Numenor anyway; or help resist Sauron but expose the Numenoreans to later corruption.

Either way, Numenor is doomed in the long run, but Tar-Meneldur acted by his conscience by yielding to his son who knows more about this matter. The events that transpired is according to Eru’s plan, ultimately.