1c was 2+ and 2N and 3H were both natural (obviously).
It's fair to say declarer didn't have the greatest start, the stiff diamond was led and declarer won and for no reason at all decided to try and cash the King of diamonds... and at trick three on a spade switch flew ace - as you do. In the end it drifted a couple of for an at the time 100% board for N/S
The more clueless part was in the post-mortem. West saw that another pair had made 3NT which was their top result at the time - and not realising that 3nt needs VERY favourable defence whereas 4H is makeable, said to her partner: "You shouldn't have mentioned your hearts. They're just as good in no trumps as a heart contract and we can make 3 no trump. 3 hearts was not a very good bid partner - you should have just bid 3 no trump
In eagles123's hand declarer can make 4♥, without finessing ♠s.
There are simpler ways, but, going for the Turner prize, declarer can play ♦A, ♥AK, ♠A, ruff a ♠, concede a ♥, win the ♥ return, and cash the last ♥, to reach this beautiful 5 card ending.
Now, East crosses to West's ♦A and leads a ♠, discarding a ♦, to endplay South, who must concede 2 of the last 3 tricks.