I do wonder why the article calls it almost perfectly circular, since it ranges from 52 to 62 AU, about 20 per cent. The Moon is on an elliptical orbit where there's about 5 per cent difference between apocenter and pericenter. :')
If those are the elements (52x62 AU), then the eccentricity works out to about 0.08, which is resonably circular -- close enough to zero so that my toolkit of "near-circular approximations" would work just fine.
The question is, how do you get an orbit that circular with an inclination that high? It's hard to think of a "capture" scenario that would work; and it's likewise hard to think of a scenario where something huge knocked this guy out of the ecliptic plane. Either way, you'd expect to see a highly elliptical orbit -- something with an eccentricity over 0.5.
There'd have to be some long-term and regular perturbation to circularize it ... but what would it be?