From my observation even as a newbie,magic attack monsters goes for opponents health bypassing their armor.Especially if there is no restriction(rulesets) in the use of their magic.
Also,you had more magic attack units than your opponent. Kudos
I went to watch the battle again I don't want to agree luck played a part.first of all from the ruleset,there is no restriction to magic attacks.You had 4 magic attack monsters against two of your opponent,that is a big plus coupled with the +1 magic from your Archon(Summoner) to all allied magic units; in this case you had Abyssal elemental,warborn shaman, mindless thrall and anasth soothsayer.Secondly, I noticed Soothsayer was doing a tank heal on Abyssal elemental,and that was a game changer. Though,you might be correct if you say luck ..But in Situations like this, Magic attacks,mostly carries the day.Anyway,thank you for the vote and engaging.More wins my wish for you.