The Auction:
Just because you have 7 hearts and only 10 hcps, don’t even think about opening 3 hearts. This hand is way too good.
East’s 2NT was ‘unusual’ showing the minors. I’m a strong proponent of having at least 5-5 for the Unusual NT and Michaels cuebids. In this case east chose to make the bid with a 4-5 because of the suit quality and favorable vulnerability. Had diamonds been the longer suit he may have started with 2D planning to bid clubs later if warranted.
South’s 3D was conventional, known as ‘unusual over unusual’. After an Unusual Notrump, cuebids in the overcaller’s suits show values in the other suits. In this case, south bid 3D (the higher suit) to show spades (5+) and game interest. Had south bid 3C (lower suit) it would be a limit+ raise of hearts.
The next 3 bids were natural. East’s 5C bid is a sacrifice at favorable vulnerability. East expects to score -300 or -500, better than letting NS make 620 or more in spades.
The play:
There was nothing to play, EW were down 2, for -500. This only netted them 30% of the matchpoints as only one NS pair played in game. No slams were bid nor did any pairs play in spades. (This was not a common game or BBO hand, so no further analysis is available).
The ‘could have been’ auction:
Since NS bid to game voluntarily, they must either double 5C or bid on, it’s their hand. South’s pass was forcing!
South has an offensively oriented hand. There’s the 6th spade and club void. Hearts are placed well with partner’s long suit behind the likely opponent with hearts if the suit breaks poorly. Diamonds are a little worrisome, but partner should be short and your Q offers some protection. As much as you would like to cuebid diamonds or support hearts, 5S is the only call.
North, knows that south is short in clubs and probably has an extra spade or two. Since there was no red suit bid over 5C, north also knows that south does not have a wasted diamond ace. I think north has an easy 6S bid here.