Satellites in Orbit are Captured ???

How much do we know about the way they came to be?(I don't) I do know
that Neptune's great Moon Triton was clearly shown to us by the Voyager
2 probe. Here is what I remember seeing. Very round white object. It
showed that Triton's surface was active. It had dark plumes very
visible,and that told us its inner part was hot and could have small
volcanoes,or like Yellow Stone gushing water,ammonia,and CO2 into its
atmosphere. Triton also is showing me that satellites are captured. It
could not have been formed in orbit. Reason for that is Triton orbits
Neptune backwards compared to the other satellites.(came in at a
different direction.) I theorize Triton was the last(after Nereid)
satellite Neptune captured,and my reasoning is its irregular orbit.
Nereid has the most elongated orbit. The older the satellites orbit,the
rounder it gets. Bert PS Triton bing hot so far away from the sun
begs this question Why?