i am 90% sure that matchmaking is forcing AFK in order to make a "fair" opponent for someone
for how many times i have seen afk in team which have obvious skill and knowladge dominance
instead of making quality matches rito is indirectly forcing quantity and in order to make game to seem balanced one gets afk .. since 5v5 would be to easy for one team (which is obvious from playing )
im watching this exact behavior of matchmaking for 3 years now... mostly the same thing-- team that has no problems in wining all their lanes without any dificulty has one afk from start... mostly match is easy anyway for the team that has AFK which also points out on how obvious the said matchmaking mechanic is