They were in a vision which of the future which is to encompass all necessary fundamentals, principles, issues, and foundation for their constituents. The constitution was broad enough to adapt to the changes and challenges that the people would face for the coming years. They have the foresight of the country which guided them to see the challenges that would come.
The framers gave the federal government the ability to change (aka amend) the Constitution over time. The ability to add in new amendments is one of the many factors that helps this document to stay relevant.
Besides the ability to change the constitution, the ability to interpret what the constitution means helps as well. For example, the judicial branch of the federal government has the power of judicial review. This allows the court to interpret whether or not federal laws violate the constitution. This ability to consistently interpret what is constitutional and unconstitutional makes the constitution an adaptable set of laws.
