Strategic bombing was pretty much a new concept in WW2. No one knew how it would work, and there were multiple schools all competing to direct strategy. The British bombed at night, thinking that hitting a city is good enough given the limited accuracy of bombers at the time, and that it reduced their risk. They simply couldn’t have precise targets, targeting a portion of a city was about as specific as they could get.
America was experimenting with this idea that you could shut down an economy but hitting some sort of key manufacturing. As an example, there was this idea that there were only a few major ball bearing producing facilities in Germany, and if you crippled them, hundreds of different products that relied on ball bearings would come to a grinding halt. That might have worked - no one really knew, and it was all speculation then. So you had these huge raids on specific industry targets.
It became clear that the transport campaign (primarily rail, but bridges, trucks, etc) was successful and so the allies leaned into it, but it was 1944 before we really figured this out. The oil campaign of 1944 was probably even more successful. Once we figured that out, the allied bombing campaign (primarily American) absolutely smothered them.
But most of the work was done by light/medium bombers and tactical aircraft flying at low and medium altitude. You could target a rail yard or an oil refinery from high altitude, but not really a bridge, road, individual train, etc. In 1944 the allies were so dominant in the air that not only could they operate with no real resistance, but they could just flood the countryside with fighters and bombers and just shoot up every target of opportunity including locomotives, trucks, etc. It was really during this stage that German transport was significantly hampered and it kind of relied on us figuring out how to conduct a proper low level bombing campaign and also effectively defeating the Luftwaffe entirely and having enough fighters, bombers, and pilots to just comb the countryside looking for things to blow up.
So, basically, no one knew how to conduct a bombing campaign at the begining of WW2, we learned on the fly, and once we saw the effectiveness of attacking transport, we did pivot to that very effectively.