Why did Sauron fear Aragons coronation?

[Aiwendil]

Originally Posted by Inziladun

That suggests that Sauron was worried enough about the idea that an Heir of Isildur remained to have in some way been looking for evidence of such a person. Aragorn, of course, does not elaborate on the "traps", but it says something that even before the War of the Ring the Heir of Isildur was on Sauron's mind.

Possibly. But Aragorn was also the Chieftain of the Rangers; and even if Sauron had no idea that an heir of Isildur was alive, he must have been aware of the existence of the Rangers of Arnor. So it may be that the traps Aragorn refers to were set merely against the commander of the northern Dunedain, with no particular thought that he might be a claimant to Isildur's throne.