A rapid scientific analysis found that fossil-fuel and other greenhouse gas pollution increased the likelihood of the storm’s high winds and heavy rains.
without climate change affecting the environment and atmosphere, the weather patterns and climate would be totally different. 'milton' would not have existed at all.
Kinda sorta; you'd still have some probability of a storm developing, so what they're doing is comparing simulated weather weather in worlds with and without the added greenhouse gases in the atmosphere, and asking "how likely is this to happen" and seeing that there are differences between the two situations.
Specific methodology for different parts of the rapid-attribution study are linked from here