Why did the founding fathers include the First Amendment in the Constitution?
They didn’t (at first). If you read the Federalist Papers you will find that the writers of the Constitution did not include a bill of rights because they were afraid (rightly so given the way courts have ruled on our rights since then) that listing rights people have may end up limiting them to only those specific rights. They finally agreed to adopt a Bill of Rights shortly after the new government was formed in order to get the constitution ratified by enough states to make it effective. More specific to your question, they guaranteed the freedom of religion because they did not want to be subjected to a state church they way England was. The rest of the rights (speech, press, etc) are primarily there to ensure the free flow of information and protect the democratic process.
