This is so complicated it rates a book...(which i've actually read), and no one can pinpoint a single reason. A lot of it had to do with government regulations which basically forced railroads to operate many lines at a loss, with no ability to close down. Other than that, Pennsy and New York Central were different "cultures" operating on different principles. Managements of both competitors were thaught to dislike eachother, and when arleady bankrupt New Haven was thrown in the mix, the recipe for disaster was complete. How i view it from a railfans perspective? I wasn't born yet when the whole thing took place, 1974, so at the end of its existence. But i would love to witness Penn Central at the trackside. With 90 plus different diesel and electric locomotive models there's not many other railroads which could compete for sheer variety. Standing at the trackside one could expect almost anything when that set of headlights appeared. Black it may have been, but there were many locomotives which wore paint schemes of original owners for some time and even the PC paint scheme had many odds, ends and variety.