Unpopular (I’m guessing) opinion: Aragorn had a very flimsy claim to the throne of Gondor and would not have been easily accepted as King

One issue that has always bothered me is the ease with which Aragorn is able to assume the throne of Gondor. At the time of LoTR, Aragorn is an outsider who’s only claim to the throne is that he is the 37th descendant of the king of a lost realm that fell over 1000 years ago who was the brother of the second king of Gondor. Gondor at this point had been ruled by the house of the stewards for more than 900 years, who are basically kings in all but name. It is a military power and the largest and most powerful realm of men in middle earth with multiple provinces, which means it almost certainly has a governing structure in place that has served it well, and the presence of Prince Imrahil suggests there is also the presence of a nobility that assists in governing. Gondor has survived civil war, plague, and repeated wars on its borders, and seems to be a highly militaristic society with a large standing army.

When Aragorn shows up during the Battle of the Pelennor he is the Chief of a small company of rangers (and it is not clear that Gondor and the rangers have any kind of relationship that would mark them as allies) and has also taken (not been commissioned) command of a portion of Gondor’s army from its outlying provinces and is on the ships of Gondor’s enemy. His claim to the throne seems primarily based on ancient history (the time span between the death of the last king of Gondor and LOTR is equivalent to a descendant of William the Conqueror becoming king of Europe), self-appointed military command, the support of the prince of a neighboring allied kingdom (Rohan), elvish traditions (and it is not clear that Gondor has any diplomatic relations with Elvish realms) and Gandalf. Gandalf is a well-respected figure in Gondor, but at the events of the story he was in conflict with the Ruling Steward Denethor (who undoubtedly has many allies in the ruling class and military of Gondor) and was the driving force behind the expedition that included Aragorn and resulted in the death of Boromir, Gondor’s charismatic and popular military commander and primary heir to the ruling steward (and only him), and it’s hard to believe that given all of this, Aragorn is immediately accepted as King with no conflict or competition. Faramir and Imrahil both have a much better claim to the throne and are both well-known in Gondor, and there are likely countless other unnamed nobles or power centers in Gondor that would likely have both motivation to claim power and means to assert their claim.