Well like the number of keys that drop in castings vary, if it's a really chatty one there are usually a lot more keys. So like, you have to be in a relatively active one, but at the same time, be the fastest at getting them. So the game was probably quite active, but everyone except Seann must have sucked at getting them.
Like a lot of times active ones will have multiple people with 5+ keys. Sounds like he just snagged almost all of them instead of them being spread out.
My castings usually last like 12-14 days theyre so long ...and one evening i think it dropped 5 keys 1 every hour ...i got super lucky :)
Never had that many before haha