Why Did Stannis Not Know About the Wildfire

[SeanBeanedMeUp]

It was clear that wildfire was a thing in King’s Landing especially since Aerys II used it a lot. Knowing this, why didn’t Stannis seriously consider that he could run into the issue of wildfire when he attacked King’s Landing? He was in the capital for a while when he was Master of Ships. He should know that the pyromancers were still around. So why didn’t he consider that his enemies would hire them to create wildfire and use it against his forces?

[Craving Peaches]

I think he had got 'overconfident' in a way after killing Renly and taking Storm's End. He puts his rather incompetent in-law in charge of the fleet, rather than someone with experience like Davos, or a member of one of the Narrow Sea Houses (one imagines they would have experience with commanding ships). He doesn't seem to suspect that the defenders are going to be doing all they can to protect the city.

Edited September 7 by Craving Peaches

[csuszka1948]

I don't think it's clear at all, a single cache was discovered.

Moreover, the defenders were only able to produce large quantities of wildfire because dragons have returned. Stannis had no way to expect it.

Finally, he was convinced that he will win (just like Rhaegar was convinced that he will win against Robert), because that's what Melisandre told him and her previous predictions all came true.