If Sannyasis are buried, not cremated then why Swami Vivekananda was cremated?

I am noticing many Sannyasis are not cremated instead they are buried. If this is the popular tradition then why Swami Vivekananda was cremated instead of being buried? I also want to know whether Adi Shankaracharya and Swami Dayananda Saraswati were cremated or buried?