Nope. Evolution doesn’t really work like that. A ‘successful’ organism simply needs to have offspring capable of producing more offspring. In the case of a parasite, it just needs to keep the host alive long enough to infect another host. Anything more than that and you start running into quality vs quantity issues. A longer living, self limiting parasite isn’t going to reproduce as fast (as size longevity goes up, reproductive rates generally go down)

A fast acting, highly transmissible parasite is generally going to outcompete slower parasites.