Blockchains attract large, sophisticated mining operations that compete against each other to win the same race. Normal people don't have enough computing power and money to compete. Thousands of miners run the race but there is only one prize. The miner that wins the race gets to produce the next block to hold a small batch of new transactions. The more miners there are competing in the race, the longer the race gets. The longer it gets, the more energy is wasted. As soon as someone wins, a new race begins and the miners keep competing to win a single prize. All the other miners lose, having wasted energy with no result. This race isn't meaningful to the transactions, it just proves that the miner did a lot of work.
