If you look at the traveller you'll see the hand was played in 4♠ twice, 5♠ four times (probably pushed there over 5♣ /♦ ) and 6♠ once (not making).

If EW play strong jump overcalls then West probably calls 2♠ over 1♦ . Without that option it's best to double intending to rebid Spades unless you find the Heart fit.

North's 2♦ over West's double is pre-emptive. This is a useful bid as it makes life harder for the player opposite the take-out double.

East has enough for a free bid in Hearts and with a LTC of only 5 South will bid at least 4♦ if not 5♦ 

North-South have done their job and by using up so much bidding space make it almost impossible for West to do anything but settle in 4/5♥ .

In 5♥ by East 12 tricks are a lay-down and if South doesn't lead the ♦ A you can make 13 by ruffing a Club after drawing trumps and discarding Diamonds on the long Spades.

If you are in 4/5/6♠ by West you can make 12 tricks against anything but a Diamond lead by drawing trumps and discarding a Diamond on Dummy's fifth Heart.

If you get a Diamond lead against 6♠ what card do you play from Dummy and why are you confident you will make 12 tricks?