The attackers were inside the system for several years. Marriott is a high-end hotel chain, whose establishments are used by state level travelers. Having ongoing access to politicians' and high-ranking corporate executives' itineraries, and especially their hotel room bookings, is an incredible avenue for espionage.

A financially motivated attacker would have tried to exfiltrate otherwise valuable data. But if the main target is the travel information data itself, and if the scope does not particularly expand over time, I am going to call it advanced espionage.