I'm sure the EU addresses it, but going strictly by Episode One, it's clear nobody had even encountered a Sith in a very long time. Possibly centuries.

One can infer from this the Jedi thought they had wiped the Sith out a long time ago. And it's mostly been sunshiny days since then, long enough to be slow to react when real evil returns. Palpatine and Maul are seeking revenge for their order, even though they weren't actually around for the events they are revenging for.

The Sith are the polar opposites of Jedi, therefore conflict.