Deregulation of rails also had massive effects down the line. There was a lot of consolidation that just made everything significantly more expensive and caused us to be more dependent on oil thanks to the massive rise in the trucking industry
The big thing that killed passenger rail in America was the US Postal Service ending it's contracts with railroads for mail services. Before that they paid a significant sum to railroads to run an RPO (railroad post office) on the trains to sort and deliver mail along the line. Simply running an RPO would be net enough income to keep woefully underutilized passenger services profitable. RPO service ended in 1978 but was in decline before then due to shifting the sorting and transport to sorting facilities and trucks respectively