Why did Aragorn take so long to make himself 👑king?

[BalrogRingDestroyer]

Aragorn was the rightful heir to the throne, a descendant of Isildur, That was indisputably so, so much that not even Denethor (who, from the books, as I'll mention in my next thread, seems more a tragic character and a decent ruler than a villain, as the movies seem to show him to be) would be able to dispute it. And getting help from his people might have helped him and his Rangers too west of the MIsty Mountains too in their work. Yet he seems content being a Ranger and wandering around like a vagabond, so much that some like Butterbur think him a bit of an odd fellow and call him Strider. Was he afraid of being attacked by Sauron if Sauron knew that he was the heir of Isildur?

 

[Aldarion]

Denethor was not evil, but he was however prideful. He will not have accepted Aragorn.

‘If you understand it, then be content,’ returned Denethor.
‘Pride would be folly that disdained help and counsel at need;
but you deal out such gifts according to your own designs.
Yet the Lord of Gondor is not to be made the tool of other
men’s purposes, however worthy. And to him there is no
purpose higher in the world as it now stands than the good
of Gondor; and the rule of Gondor, my lord, is mine and no
other man’s, unless the king should come again.’

‘Hope on then!’ laughed Denethor. ‘Do I not know thee,
Mithrandir? Thy hope is to rule in my stead, to stand behind
every throne, north, south, or west. I have read thy mind and
its policies. Do I not know that this halfling was commanded
by thee to keep silence? That he was brought hither to be a
spy within my very chamber? And yet in our speech together
I have learned the names and purpose of all thy companions.
So! With the left hand thou wouldst use me for a little while
as a shield against Mordor, and with the right bring up this
Ranger of the North to supplant me.
‘But I say to thee, Gandalf Mithrandir, I will not be thy
tool! I am Steward of the House of Ana´rion. I will not step
down to be the dotard chamberlain of an upstart. Even were
his claim proved to me, still he comes but of the line of
Isildur. I will not bow to such a one, last of a ragged house
long bereft of lordship and dignity.’
‘What then would you have,’ said Gandalf, ‘if your will
could have its way?’
‘I would have things as they were in all the days of my life,’
answered Denethor, ‘and in the days of my longfathers before
me: to be the Lord of this City in peace, and leave my chair
to a son after me, who would be his own master and no
wizard’s pupil. But if doom denies this to me, then I will have
naught: neither life diminished, nor love halved, nor honour
abated.’

And Aragorn was not an idiot. He knew his history, how Gondor had rejected Arvedui, and likely surmised that Gondor accepting him merely because of his lineage was highly unlikely. And he will have been familiar with Denethor personally, as well, from his service as Thorongil.

He certainly was afraid of being attacked by Sauron - after all, he knew that Sauron was searching for the heirs of Isildur - but I think he was even more afraid of potentially inciting another Kin-Strife in Gondor. In fact, he himself says as much:

But E´ omer said: ‘Already you have raised the banner of
the Kings and displayed the tokens of Elendil’s House. Will
you suffer these to be challenged?’
‘No,’ said Aragorn. ‘But I deem the time unripe; and I have
no mind for strife except with our Enemy and his servants.’
And the Prince Imrahil said: ‘Your words, lord, are wise,
if one who is a kinsman of the Lord Denethor may counsel
you in this matter. He is strong-willed and proud, but old;
and his mood has been strange since his son was stricken
down. Yet I would not have you remain like a beggar at the
door.’
‘Not a beggar,’ said Aragorn. ‘Say a captain of the Rangers,
who are unused to cities and houses of stone.’ And he commanded that his banner should be furled; and he did off the
Star of the North Kingdom and gave it to the keeping of the
sons of Elrond.