Inconsistencies in the book

They were all busy elsewhere. I don't think it was a lack of concern, but as said a lack of means. They did help where they could. Also remember they had already fought the prequel to this war in the Last Alliance, and it may very well be that they all knew why he was back. And remember Sauron was but a servant of a greater evil, so not persay the greates threat. Still the most pressing issue at the time. Remember it was said a number of times that Sauron's power was growing and so they needed to get rid of the ring before it was too late. It's not too much of a jump to say he granted more power to his general to take Minas Tirith.