Introduction to Rugby: Uncontested Lineout Mauls

Uncontested lineout mauls can be confusing for fans and players alike, because so many things are happening at once.
This video explains what the actual elements needed for a good outcome for the defense are: 1) ball transferred back too early, 2) no physical contact with the "not-yet-a-maul" pod 3) pod moves downfield and comes in contact with a defender, who is effectively obstructed.
If Larsen hadn't been run into, Thiebes's tackle would still have earned the Free Jacks a turnover. Great outcome for New England -- it went exactly as planned.
Game management guidelines tell referees to treat it as the ball carrier running into the back of his own player (so a scrum) rather than full obstruction (a penalty), which is why the sanction is a scrum to the Free Jacks.
Then we have a clip from Atlanta looking at why this tactic does not always pay off, namely when the mauling team notices and waits to transfer the ball to the back.
Technically Atlanta had too many men bound on to the ball carrier (the early bind called a "latch" is now limited to 1 teammate, a recent change) but you are almost never going to get that call as the defense when the other team at the lineout was binding up to form a maul. I've never seen it called in this situation -- only in open play.
Hope that helps to clear things up! If I got something wrong, let me know and I'll do my best to correct it.

[@ragdoll2309]

One of the first time I saw this was when Ireland were taking on (I think) South Africa. It's not so common at international level for the team not to contest the lineout maul and it ended up going Ireland's way, but as you showed, if the players were more alert to the strategy then it could have easily gone the other way.

[@miklmiklmtrcycl6009]

Should not the ref have called Atlanta for a flying wedge?

[@yetipoetrugby5932]

The ref could call that, as it is similar. But usually a flying wedge happens with a free kick or penalty kick, and is more dangerous (players moving faster with a much bigger gap between them and defenders, making it impossible to contest safely). At the lineout, it is simply ruled as obstruction and the defenders awarded a scrum.
Edit: I misunderstood your question, I'll look at that play later and give an answer

[@yetipoetrugby5932]

Okay, sorry for the delay! The reason this is not a Flying Wedge is that a Flying Wedge is defined only as something that occurs on a penalty kick, free kick, or in open play. At a lineout, we are not in open play until the lineout ends (which happens when the ball leaves the lineout or a maul travels a set distance from it). That is when the backs can come up to defend, and at that point forming a flying wedge would be illegal. But until then, it is allowed, I would guess specifically to keep this tactic viable and make the "no contest maul" less desirable choice for defenses, and because it is not really a dangerous tactic when the other team is 1 meter away and ready for contact.
www.world.rugby/the-game/laws/definitions/#laws_let6