To be fair the same could have been said about Goldberg. Really, the reason is that whether you hate him like I do or love him, in which I don't understand, Brock draws money, and what does Vince love more than any thing Money.
It´s never good when too much faith is put in one man. Like Goldberg, Brock Lesnar was impressive, but now he´s being overused so infrequently and achieves so much without working full time, that soon there won´t be anything left for him to do. Brock´s beaten the best, broken records and elevated himself very high above everybody else. WCW suffered in a way because Goldberg almost demolished everyone. He disrupted the careers of many, Steve Mcmichael, Glacier, to name a few. Scott Steiner beating him helped redress the balance and even though Scott dominated, he never burried all his opponents. They came back and rejuvenated themselves later, but Goldberg just caused a landslide that nearly took everyone with him.
Which clearly, Brock Lesnar is on the verge of doing.