https://blockchain.info/tx/81f749304a58590b5124cfb9758848fa71d14162dad8c844c1ecdfc9b0d9ba53
How is it possible at the current network busy?
Just guessing here, but many of the inputs you used were "older" and +1 BTC... So this transaction must have had a rather big priority... Maybe you got lucky and were included into a block by a miner that still reserves some space in their blocks for a high priority transaction? It's rather rare nowadays tough, and i can't imagine that this transaction would have had one of the highest prioritys in the mempool either...
Or maybe you just got lucky period