Originally Posted by
Mechalich
Arrogance is part of it, but the Jedi of the PT are also guilty of trusting the Force too much. They spent time with the clones and came to know them in the Force. Through the Force the clones were revealed as loyal, valorous, and dedicated to the principles of the Republic, something the Jedi had, themselves, worked to instill in them. At the same time, the Force hid the future in which, due to the activation of the biochips, the clones would undergo fundamental personality changes (the Bad Batch makes it quite clear that the clones behave very differently post-activation) and murder them all. This is, of course, the same mistake Palpatine makes in the OT. He trusts the Force's revelation that there's no threat on the Forest Moon and completely misses the possibility that the Ewoks would side with the Rebellion and support the attack on the bunker, which is ultimately his undoing. It's the same mistake - arrogantly trusting the Force instead of properly planning out contingencies - from the opposite side.
Ironically, given Lucas' stated goals to increase spirituality via Star Wars, both trilogies hold the same lesson: don't trust mystical insight over hard evidence and sound preparation.