The Long Beach PE line *was* owned by a public agency at the end. It (and the LA Transit trolley buses) were inherited by a prior incarnation of LAMTA from the private companies a few years before the end. But they were a "bus company" - public, but at that time public transit meant diesel buses not streetcars or anything else that required infrastructure reconstruction and maintenance. And the PE LB line desperately needed both - which there was no money for. You can say all kinds of "could haves" and "should haves" but at the time public transit money was almost all local and every penny was pinched. That's simply a historical fact, regardless of conspiracy theories which are now moot. Rail and electric transit had No Future in that kind of operation. It was only in the late 1970s and early 1980s that federal and state transit support started appearing in useful amounts.

On the other hand, somehow (because SP still used some of it for freight service perhaps?), the LB PE line wasn't totally torn up and the r/w sold off. That's kind of a miracle. So when the new light rail systems came around (with federal funding) there was a place to put one without spending unbelievable amounts of money for land. LA followed that model with all of the other light rail lines outside of downtown except for the East LA Gold Line extension and the Green Line - buy up a lightly or unused freight line (OK, ATSF carried *some* passengers through Pasadena but not much local traffic) and convert large chunks to light rail. The Green Line was built for them by Caltrans as part of a freeway project, as very expensive "mitigation" for car exhaust, so it doesn't count in the overall scheme.