He had evidence though? He had recordings of them. He had the Jade Raven. He had his own and Master Fay's testimony, which the Council can confirm is true via the Force.... that's more than enough. They clearly believe him, they just thing the Vong are chumps if one padawan can mess them up.... nevermind he's a once in a millennium talent, with extensive Mandalorian training and weapons.... and he didn't actually win anyways... Some of the arrogant dicks on the council, who couldn't fight for shit anyways, just make an assumption and move on so they ponder their own wisdom for another couple decades.
Are you referencing his Observe knowledge he gathered from the Vong? That's the only additional knowledge he has on them.