You can't focus on something you don't know.
That's simply not true. The entire purpose of establishing priority intelligence requirements (PIRs) is to find out the things you don't know. Note that there's a difference between something being unknown and something being unknowable.
The planning process starts with defining the commander's objective. Once that's understood, a staff estimate is created which documents the facts (things that are known), assumptions (things that are thought to be known), intelligence gaps (which encompasses both unknown and unknowable information), constraints (things the force must do) and restraints (things the force must not do). The intelligence gaps drive the creation of PIRs. The staff estimate process was well understood and practiced during WW2.
The key problem for the Germans is that their planning process was crap. Senior Nazi leadership tended to work on assumptions rather than facts. Even when a sound operational plan was developed, the tactical focus for German forces tended to overcome the intent. The classic example is the Blitzkrieg into France in 1940 with the tanks outstripping the infantry, which was absolutely not what was planned. That over-focus on the tactical environment severely limited Germany's efforts at operational or strategic planning...one could argue that the latter seldom, if ever, happened.
Germany knew about the RDF sites and conducted the world's first airborne ELINT collection against them in 1939. After the fall of France, SIGINT sites were set up on the French coast to intercept British transmissions. Greater effort could and should have been devoted to understanding the role of these sites. As it was, the Luftwaffe did attack them and the British clearly thought that German SIGINT was listening in, otherwise why bother trying to deceive that a non-operational site was still functioning?
The location of RAF airfields was also known. Even to this day, it's easy to identify a 1930's expansion-era RAF airfield because the buildings were all built to the same patterns. You can go to any 1930s RAF officers' mess and know exactly how to find your way around because they used the same layout...it was the fastest way to build airfields. Guardrooms, MT yards, POL facilities...all had a very similar appearance across the different airfields. The target sets I selected (maintenance facilities, POL etc) specifically impact the ability of the force to operate. You can disperse the operational aircraft to satellite fields but, at some point, they will require a major service. Hinder the ability of the maintenance crews to perform that function, and force strength suffers. This is not hindsight, it's common sense based on the way all air forces operated at the time.
Of all the target sets that I identified, the only truly unknowable one was the location and purpose of the Sector and Group Control Centres. Luckily for the Germans, if they'd targeted the maintenance and other support areas of 11 Group airfields, there was a decent chance that they'd hit at least part of the C3 infrastructure. Yes, the facilities could be (and were) dispersed away from airfields eventually...but that still imposes an operational cost. Also, the benefit of the Sector/Group Control construct is heavily dependent on RDF. Lose RDF and you're back to the Observer Corps, which reduces warning and would greatly hinder the ability of 11 Group to respond in time to intercept. It also would likely put more strain on the aircraft as they tried, in vain, to gain altitude...which further stretches your maintenance facilities.
None of this is hindsight. It was all entirely knowable at the time. The simple fact is that the Nazis didn't take the time to conduct operational planning.
The Luftwaffe wanted to destroy Fighter Command, so it attacked aircraft factories, which it thought it knew. For example yesterday, 80 years ago, the Boulton Paul factory in Norwich was attacked when Wolverhampton would have been a better target. During WW2 Boulton Paul in Norwich took on the unglamorous role of making prefabricated buildings for the armed forces, not a vital target for the Luftwaffe in 1940.
Now we're back to using a tactical force for strategic effect. Destroying Fighter Command is a strategic goal that is impossible to achieve. It's like a partially filled balloon - squeeze it in one area and it only bulges somewhere else. Gaining air superiority over the approaches to London is a much better goal and is much more achievable.
Similarly, aircraft factories are strategic targets. If you want a quick operational victory, you don't hit factories. You go after the front-line forces and deny them the ability to operate. Again, Germany was using its tactical air force in an effort to achieve strategic effects and that's a really hard thing to accomplish.
It also went after British aerodromes because they were identifiable targets. It couldn't even focus on RAF aerodromes never mind Fighter Command stations or 11 Group's sector stations, because it didn't know which they were.
Have to disagree here. As noted above, RAF airfields are easy to identify and, as others have observed, Germany had plenty of pre-war reconnaissance imagery to work on. The fact that they didn't is a failure not only of intelligence but also of operational planning...which is the entire point I'm making. You don't even have to hit all the 11 Group airfields. You just need to hold London at risk. Drive through a path to London where RDF can't see you and the defending airfields are at low levels of operational capability, and you have the elements necessary for an operational success.
The point is you do know all these things, with the benefit of hindsight, and could therefore employ your Luftwaffe far more effectively. You or I could probably win the Battle for the Germans, with the knowledge we have today.
Yep, hindsight is a wonderful thing!
Hopefully, I've explained myself sufficiently to make it clear that all my assertions were entirely knowable at the time. The fact that the Nazis failed to capitalize on knowledge that was there or could be readily obtained is something for which we should all be eternally grateful.