People who belong to this social group are much more determined to make it in life.

make 在这里是动词，意思是"实现、达成"。 it 是代词，指代前文提到的"成功"或"成就"。 make it 是一个固定短语，意思是"取得成功"或"达到目标"，常用于描述克服困难后获得成功的情况。