They have it mixed up.

[Anamatar IV]

i just saw it for the 9th time and just realized that pj mixed it up when they were on cahadras. in the book aragorn led them onto the mountain but in the movie gandalf didnt want to go to moria and aragorn did.

[EverEve]

can you explain that to me again? didnt quite catch it the first time!

[Niniel]

He means that in the book Gandalf wanted to go to Moria, but Aragorn didn't want to, because he has a feeling that Gandalf would be killed ('it is not for any of us that I fear, but for you, Gandalf', or something), while in the film Gandalf doesn't want to go to Moria unless there is no other choice, while Aragorn is not very anti-Moria.