Peak electrification in the US was in the 1930s and began falling in the 40s, but the Class I railroad route miles were almost 2.5x that of today. Electrification generally came about to reduce the impacts of steam traction (e.g. in cities and tunnels), to gain more power on grades, or to reduce the opex on high-traffic routes vs. steam.
In the decades after WW2, diesel-electric propulsion boomed, viable again after wartime shortages were over, simpler to maintain than steam, and more flexible than electric. This was well before double-stack trains got started in the 80s, but now that double-stack is widespread in the US, overhead electrification does present another operational hurdle.
In the decades after WW2, diesel-electric propulsion boomed, viable again after wartime shortages were over, simpler to maintain than steam, and more flexible than electric. This was well before double-stack trains got started in the 80s, but now that double-stack is widespread in the US, overhead electrification does present another operational hurdle.