Answer: No, you didn't do anything wrong. Once the hyacinths have finished blooming the flowers will fade and the stems will topple over. You can cut the stems off the plants but leave the foliage alone. It will die back on its own as the bulbs go into dormancy. You can keep the bulbs in the container or you can plant them in the ground. They will rest all summer and most of the winter. In late winter they will wake up, develop roots and you should see some leaves emerge. With any luck at all, they will flower again for you next spring.
Hope this answers all your questions!
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