The key development that led to the eventual construction of the computer was Moody's invention of a new type of flip-flop circuit, a key component of all computer systems.
One downside, only realized later, is that the current draw of the flip-flop was not balanced, so storing different numbers in them could lead to dramatically different current needs on the power supply-something that should be avoided wherever possible to reduce noise generated when the power draw increases or decreases.