Why can they take the cooler weather? Because nature made them that way. That’s the short answer. Not very informative but accurate.
There are several threads on here where broody hens raise their chicks even in weather sometimes below freezing. The chicks leave Mama and her warmth to eat and drink, dust bathe, or just play. When they get cold the go to Mama and warm up. How long they stay out away from Mama’s heat depends on the temperature and how old they are. Newly hatched chicks tend to spend their first two or three days under Mama a lot but after that they get really active. Mama can also raise them when the ambient temperature is above 100 but that’s not your question. That hot weather is more dangerous than the cold weather in some ways.
A lot of us brood outside. I candled last night and will put 26 eggs in lockdown tomorrow night. The weather forecast predicts nighttime lows below freezing with daytime highs in the 40’s when I’ll probably be putting them in the brooder in my coop. I’ll keep one end of my brooder plenty warm, even when the ambient temperature is below freezing. Some mornings I’ll probably find frost or ice in the cold end. Later the forecast calls for days in the 60’s. My warm end will probably be too hot then. It doesn’t matter, at some distance away the chicks will always be able to find a spot just the right temperature for them to warm up if they are cold and cool off if they are hot. When they get older they will spend a lot of time in the cold end or the hot end. Some people would be surprised at how much time that is, but as long as they have some place to go that has the right temperature for them they do fine.
To me the ideal brooder is one that has one area warm enough and another area cool enough. That keeps you from cooking the chicks or freezing them. As long as they have the option they do great at self-regulating their temperature needs.