I'm glad the solution worked! Let's break down what happened and why it worked, which will help you understand the entire Spring Boot + Hibernate Spatial + GeoJSON + PostGIS stack better.
You were experiencing an issue where your Point geometry field (cityCoordinates) wasn't being serialized correctly to JSON. Instead of getting a proper GeoJSON Point representation, you were getting a deeply nested structure with repeated "envelope" objects:
"cityCoordinates": {