Why won't she start!

[1963chevyc20]

I got a 1963 c20 in may of 2013. I let the truck sit and ran it matey 2 times in a year. I replaced the fuel pump and gave er fresh gas and charged the brand new battery I got with the truck. It was flat out dead from playing music without starting it. I charged it just enough to start the truck. I drove it just down the road. I came back shut her off and 10 minutes later came to start it again. It cranked and the battery died. Why won't she start!