Jupiter and its moons are a billion miles from the sun — more than ten times Earth/Sun distance. Surface temps on Ganymede vary between -170 to -290 Fahrenheit. Water at that temperature doesn’t just freeze — it rivals steel in terms of strength. Ganymede may have liquid water beneath the ice layers covering its oceans from geothermal sources. But on the surface? Not a chance.
That IS the case NOW... But the most normal situation in the Milky Way is for gas giant planets to be up close to the stars they orbit, hence the term "hot Jupiters" that you read. That WAS the situation with Jupiter a few tens of thousands of years ago. You might wanto to watch that 20-minute intro.
The event in which our present sun captured that ancient Southern/Saturnian system caused everything in our system to pile up in a sort of a heap temporarily, and then everything spread out to eventually become what you see now.