WARNING! SOME SPOILERS AHEAD!!
MQC = Master Quest Cape
When the MQC was released, there were some players who found it strange that Curator Haig Halen at the Varrock Museum would be the cape seller.
Afterall, the Wise Old Man sells the quest cape. He was a big time adventurer right?
Others quickly (and wrongly) assumed that Haig was for some reason a member of all the different adventuring guilds and done other quests and had levels and stuff.
Why is this wrong?
Well, as Jmods pointed out, Haig had his own adventures and lessons in life to learn about.
The MQC is about lore and history. The Varrock Museum is steeped in it. They spend their whole time earning about the history of the world. The large library in Varrock is nearby as well, adding even more resources for them.
Haig, as the head of the museum, would be one of the first people to understand the world.
How did he get there?
While the World Guardian is handed out information from others, and digging up tomes from abandoned areas, doing much of the dirty work (but also sometimes having fight dragons and demons to get the knowledge), Haig would have still gotten his hands dirty.
Sifting through panning trays, looking at abandoned temples, studying old dusty scrolls.
Sure, he's probably not as well traveled, or faced any major dangers in his work, but he still found his own way of getting there.