So these 3 are basically the cause of all this or somewhat the start of everything...
To be fair, the only thing the Tohsaka did was provide the land for the Grail War. If they hadn't the Einzbern and Makiri could have just held it somewhere else. So, really, it's the Einzbern and Makiri/Matou clans' faults, especially the Einzbern, who wrecked the system with their idiotic cheating attempts.