The Constitution was mainly written by wealthy, educated men like landowners, merchants, and lawyers who had property and political power. The lower class, like poor farmers and laborers, were mostly excluded, along with women and enslaved people. This shows there was a big difference between the wealthy class that had power and the lower class that didnt have much of a voice. 

I think the class structure was different from today because back then wealth and property had a much bigger role in who could participate in government. The writers were also afraid of democracy because they worried the poorer majority could gain power and make changes that would hurt the wealthy peoples property and money. They wanted to protect the social and economic power they already had.