How could the Nazgul take Minas Morgul?

[Damrod]

I'm a little confused about what Boromir88 said about this-

the Council of the Wise begin to start watching out for Sauron more, as the siege upon Minas Ithil seems to be rather passed off as 'unimportant.' And people don't start worrying about Sauron until half a century later.

Wouldn't the Wise be concerned about this--a full assembly of the Nine, on the doorstep of Mordor, besieging one of the chief cities of the South? Especially since they're 'watching out for Sauron more'. I don't really know myself, I mean, all we have to analyze are a couple dates and vague references. Perhaps the answer was Numenorean pride:"We've got this Minas Ithil thing managed. Gondor can solve its own problems!"