Structure pieces have hit points and depending on what material was used depends on how many hitpoints. It's all breakable and if they likely had good tools or weapons that produce high damage or they had to much time on their hands and grinded hitting the structures and such.
Just a guess, but they either intended to troll by destroying everything OR they realized they couldn't loot storage successfully and only destory it so they got mad and took the time to wipe everything out. Most folks would just break in and grab what they could and leave...less risk that way of the owners coming back online or coming back from an adventure and catching them in the act.