Brock did not know that Walt poisoned him. In fact, no one knew except for Walt himself.
To understand this, let’s go back to the events leading up to Brock’s illness. Jesse’s girlfriend, Andrea, had an open pack of cigarettes that Walt had access to. Walt removed one of the cigarettes and substituted it with a ricin-laced one.
Walt’s plan was to make it seem like Gus Fring, their mutual enemy, had poisoned Brock. By doing this, he hoped to turn Jesse against Gus and solidify their alliance. Walt’s ultimate goal was to eliminate Gus and take over his drug empire.
So, when Brock fell sick, Jesse immediately suspected that Gus had poisoned him. He had no reason to suspect Walt because he believed that Walt was on his side. Walt played his part perfectly, acting shocked and concerned about Brock’s condition.
But here’s the twist: Walt had actually orchestrated the entire thing. He made sure that Brock would get sick, but not to the point of death. He wanted Jesse to believe that Gus was capable of such a heinous act, which would ultimately lead to Jesse turning against Gus.
Walt’s plan worked, and Jesse became consumed with vengeance against Gus. It wasn’t until later that Jesse discovered the truth about the ricin cigarette, but by then, it was too late. The damage had been done, and Walt had successfully manipulated Jesse into doing his bidding.
Throughout this whole ordeal, Brock was an innocent victim caught in the crossfire. He had no idea that Walt had orchestrated his illness, and he certainly didn’t know that Walt was responsible for poisoning him.
In the end, Walt’s long con paid off, but at a great cost. He sacrificed the innocence of a young boy and manipulated his closest ally, all in the pursuit of power and control. It’s a chilling reminder of how far Walt was willing to go to achieve his goals.