While he had significant shortcomings (Peter Keating once described him as a fraud who didn't live up to his reputation), Guy Francon is also shown to have significant redeeming characteristics, such as his genuine love for his daughter. He is later seen sitting in support of Howard Roark at his criminal trial along with Dominique, for example.
Even professionally, he ended up not being a _complete_ fraud (even though he did little of his own designing later in his career). For example, he was really good at finding clients, to the point that Peter Keating had to acknowledge that there had been a method to his madness all along.