Why is a WILL called a will

I think a will cannot be different from what you are living. Essentially it is just that you trust a few people to carry out what you would have done if you were living. Hence if you plan to give away all your money to charity once you are dead, you may want to do the same while you are alive.

I believe a will is about ensuring that all your "material" possessions are properly distributed as per your wishes to the relevant people. I also believe that a will is not about carrying on your legacy. If you want your lifes work to continue after your death, you would want to establish an organisation (system) which will continue to function as per your established "vision" even after you are gone.

It may not be a great idea to document your ideas in a will, while expecting that someone will work on them while you are gone. Its rare. People have their own "wills" to live by.

You may document your vision and share it with people. But at the risk of repeating, you may want to establish a system which will execute on these ideas even while you are away. E.g. a business, a trust, an NGO, a political party, etc (if you really care about these ideas to persist)