In some cases it is obvious enough why Jackson did what he did, and it seems right.
In some cases it impossible to see Jackson's reasoning.
I some case what Jackson does makes no sense.
Aragorn did pick up the shards of
Narsil and replace them. I sensed no fear there.
Maybe I was supposed to sense fear. I don't know.
As to why the
sword was not forged before Aragorn set out from
Rivendell ...
The subject has not come up in the film.
But the sword has been unreforged for a thousand years and more now.
Why should anyone suddenly think of reforging it within the logic of the film? There is apparently no prophecy in the film
Middle-earth that the sword is to be reforged when
the One is found.
We know Jackson has decided that movie-Arwen will come in person to movie-Aragorn either with her two brothers or more likely instead of her two brothers.
She as likely as not she will bestow the sword on Aragorn then, with or without that embroidered banner.
Jackson may connect this to the kingship.
Or it may simply be shown that
Elrond, influenced by
Galadriel's telepathic message, has reforged the sword and sent it to Aragorn to aid him in his tasks.
I suspect that it will turn out that
Arwen and that host of
Elves from Rivendell are not heading for the Havens, but indeed have been sent to aid Aragorn, for Jackson never did make a clear end to the debate between Elrond and Arwen.
They will not take even ten days to seek out and find Aragorn.
Jackson might plan to use the sword as simply another way to increase the importance of the Aragorn/Arwen subplot.
But I could certainly be wrong in all this.
One might try asking the next person who claims that Jackson
had to do something what it is that Jackson
has to do in this matter.