BATTERIES, OH THOSE BATTERIES!
The problem in those times were the batteries. In the 70’s or 80’s the first battery packs, powerful enough for full aircraft propulsion system, weighed more than 500kg, which was more than aircraft could carry.
Although lithium batteries appeared to be a new introduction to the battery market, they were originally experimented with already in 1912, but it was not until the 1990s that the first commercially available lithium batteries came on the market. Those were very small batteries, primarily designed for the photographic industry.
In 1985 a rechargeable and more stable version of the very first lithium battery was commercialised by Sony and released publicly in 1991; and In 1997 the first lithium-polymer batteries were introduced, followed by lithium-ion batteries. The first batteries, both strong enough and light enough to be used in aviation, appeared for power applications in 2005-2006.