We Are Going to the Moon, Again. Why Did We Stop?

How exciting that we are going to the Moon again, but this has been done before.  Why did we stop?  If we had not stopped we would be on Mars by now, and the Moon would be a Thruway 
rest stop with a McDonalds. If we got to the Moon in 1969 with a Lunar Module made of tin foil and a space ship with less battery power than your phone, you would think it would not be a challenge to get back.  I mean they must still have the old plans? 

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