They paid some of those sources for the information they wanted. But some legendary telepaths were willing to tell what they wanted to know for free.
After getting information from many sources and analyzing them, they realized that the bartender had spoken some truths. But he had also omitted some critical information and lied about others.
The bartender had been truthful about why no one could control the Mind Palace for so long. He was also truthful about how the virtual flesh came about and why information about the Mind Palace could only be carried by the mind.
He had also spoken the truth about why Gerald died and the importance of the virtual flesh to subduing the Mind Palace. Even the theory of how the virtual flesh could be used to control the Mind Palace was the truth.
From what they gathered, a powerful telepath had indeed paid many legends to buy off their control of other telepaths. So the bartender wasn't the one that truly wanted Gerald dead.
