Let's have a quick look at this wikipedia map of the Bismarck's sortie to view the geography

German naval construction occurred in the North German ports like Hamburg, Wilhelmshaven and Kiel. If you look at a map of the North Sea, you'll find that these ports have two exits to the Atlantic ocean proper, the English Channel and the northern passages on either side of Iceland, which were later called the Greenland, Iceland, and UK (GIUK) gap.

The English channel exit was very close to the RAF bases, heavily mined, and easier for British naval units to close. Although the German Navy did push Battlecruisers thru the channel (in the other direction), it was a very difficult operation. Going back to our North Sea starting point for the Bismarck and Tirpitz, we can see that the Norwegian coast near Bergen and Trondheim is actually the closest German occupied territory to the northern exit to the Atlantic.

Stationing German battleships and battlecruisers in Norway meant they were a constant threat to breakout to the Atlantic. After the summer of 1941, the US and UK also ran supply convoys to the Soviet Union via the Norwegian sea and the Arctic. Stationing naval units in Norway also gives them the most immediate threat to the Arctic convoy routes, a key German objective since the Eastern Front was the most active theater of the German war effort. While the Fjords are not ports, they are very close by sea to the Norwegian ports of Bergen and Trondheim providing most of the services the ships needed except for serious repairs.

A "fleet in being" is a strategic concept that says that even if your ships don't leave port they can force the enemy to be prepared to counter sorties. For the period 1942-45, the German navy was forced to adopt this strategy by severe fuel shortages and the fact of Allied naval dominance. By parking Battleships and Battlecruisers near Norwegian ports, the Germans forced every convoy between Halifax and the UK and the UK and the Soviet Union to be heavily escorted and for a force of British battleships to be constantly available to sail from Scapa Flow and unavailable for operations in the Mediterranean or elsewhere. From the German point of view, this was about the best plausible strategic use of the ships, which in any case became increasingly eclipsed by air power as the war progressed.

The relocation of Tirpitz and other surviving heavy units into the Norwegian fjords was the result of the failure of the Kriegsmarine's surface strategy. As /u/white_light-king correctly points out, the Norwegian theater was arguably the best place to have such a fleet in being and the surface units could be defended more easily. But the Kriegsmarine only reluctantly adapted their Norwegian bastions after the prospects for heavy surface units in the Atlantic dimmed considerably.

Kriegsmarine chief Raeder and the the Naval War Staff initially looked at the fall of France as a chance to break out of the geographic constraints that had forced the Kaiser's navy to remain in German ports. Although they recognized that the RN's material superiority was a given, there was an assumption within the surface officers of the Kriegsmarine that German heavy units based in French ports could sortie at opportune times and achieve local command of the ocean. Although U-boat chief Karl Dönitz contended that the U-boats were the only tool available to the Germans, Raeder and his staff envisioned using heavy surface units as a way to unbalance British naval superiority and force the RN to redeploy units. Basing heavy units at the French port of Brest would geographically place them in an area Germany could defend, but also where German units could quickly sortie and reach the Atlantic shipping lanes. This asymmetric warfare would keep the RN reactive and on the defensive so that it could not use its naval superiority coherently. The sortie of the Gneisenau and Scharnhorst in January-February 1941 as well as Admiral Hipper's two sorties seemingly vindicated this stratagem. These heavy units managed to hunt down and sink a number of British ships without losses and they forced the RN to scramble and redeploy their own units. This would weaken convoys and the Mediterranean forces, allowing the German and Italian forces to operate more freely in these regions. Bismarck and Prinz Eugen's ill-fated breakout into the Atlantic, Exercise Rheinübung, was an attempt to further capitalize on using the heavy units to extract a disproportionate response by the RN.

The sinking of Bismarck during Rheinübung illustrated the problems with this strategy. The RN did have more than enough surface units to react to the appearance of German ones without fundamentally disrupting its convoys. In some ways, Raeder's plan to use heavy units to unbalance British forces worked only too well. The RN devoted considerable effort to not only hunting down these heavy surface raiders when they appeared but also their support ships. The summer of 1941 witnessed a determined effort by the RN to hunt down the various support ships of the Kriegsmarine such as tankers or weather ships. Ultra intelligence helped greatly in this endeavor and it made any Brest breakout much harder to achieve. The commando raid against the St. Nazaire docks by an explosives-laden destroyer further underscored both to Hitler and the Kriegsmarine the vulnerabilities of heavy units based in France.

Hitler himself was growing increasingly skeptical over the value of battleships and other heavy units in light of airpower. He only barely approved of Rheinübung and Bismarck's loss justified these doubts. For all his military dilettantism, the German dictator did appreciate the political ramifications of sinking these heavy units. Battleships still had heavy cultural associations of national power and prestige. A loss of one of these capital ships may not have had an impact on the wider naval war, but it could damage morale and give an impression of national weakness. Thus the Brest-based units found that Hitler would not really authorize operations that carried excessive risk.

The problem was that the asymmetric style of warfare the Kriegsmarine was pursuing with its surface units was inherently a risky venture. But the Brest fleet did not need Hitler to hamstring its operations. In addition to its losses of support units, the Kriegsmarine could not supply these ships with enough fuel to keep them at operational readiness for the latter half of 1941. It was becoming increasingly difficult to keep these ships ready at port, and sorties in the Atlantic were becoming increasingly costly in terms of fuel. An estimate by the Quartermaster's Department of the Naval War Staff in late 1941 pegged the fuel costs of a surface ship operation at 72000 tonnes of fuel, which exceeded the monthly allotment of fuel from domestic sources by some 20000 tonnes. The increasing number of air raids on Brest and other ports likewise cut into the limited resources available to the Kriegsmarine. The RAF lacked the ability to sink these units at port in 1941 and German air defenses made these attacks quite costly, but they could damage these surface units. Unlike the U-boats, these ships could not be placed in ferro-concrete pens that were bomb-proof. Repairs to the surface units, whether through British actions or just normal wear and tear, threatened to over-strain the repair infrastructure of the Kriegsmarine in France.

Not surprisingly, it was Dönitz who first broached the idea of a strategic retreat by the surface units to either Norway or German waters in November 1941. Raeder tried to hold a rear-guard against this move, but the logic of a retreat gathered steam by the winter of 1941. The sinking of Force Z by Japanese planes as well as the Pearl Harbor raid only reinforced Hitler's increasing skepticism about the ability of battleships to survive against modern aircraft. The stalling of Barbarossa also contributed to this decision as relocating German surface units to more easily defended areas would mean they would gobble up less resources and could be laid up if need be. One of the signs that the winds were changing against the French-based fleet was the Hitler was insistent that the newly-completed Tirpitz not breakout into the Atlantic like her sister, but rather stay in Norwegian waters. The St. Nazaire raid may have denied Tirpitz a French dry dock, but there was already some thought being given to keeping her safe and away from British forces. Time was thus running short for the Brest squadrons. Escaping via the Channel may have been risky but it was a better alternative than rusting out in Brest. As Hitler put it to Raeder in a January 1942, the Brest fleet was like a cancer victim:

who is doomed unless he submits to an operation. An operation, on the other hand, even though it may have to be a drastic one, will offer at least some hope that the patient's life may yet be saved. Passage of our ships through the Channel would be such an operation. It must therefore be attempted.

Raeder reluctantly bent to the need for a strategic retreat but a number of other officers came to the same conclusions as Hitler and Dönitz. The Kriegsmarine's representative at OKW Heinz Assmann wrote a postmortem on the French-based ships noting, "Brest was strategic-operational wishful thinking which was not fulfilled, and could not be fulfilled in future owing to enemy air superiority."

The "Channel Dash" actually succeeded in the face of British efforts was one of the last real successes for the surface fleet. The Kriegsmarine did attempt to replicate its asymmetric warfare in the Arctic by using the threat of German heavy units to destabilize British operations in this area. Yet the same pattern that characterized surface units in the Atlantic reemerged in Norwegian waters. Heavy units were able to achieve some degree of success, most notably the threat of Tirpitz was one of the reasons for the scattering of the PQ 17 convoy. But the British and the Americans were more than able to meet this reduced German force with heavy units of their own. And by the same token, the British were willing to spend inordinate amounts of resources to disable these units such as midget submarine attacks and Tallboy bombs. This pressure plus the fuel squeeze made the German surface units increasingly port bound, the main difference was that unlike 1941, there was no safe retreat and Allied attacks on these units were far more effective than those earlier in the war. The Kriegsmarine's strategic retreat from France may have been successful, but it was to a backwater, and from 1943 onward, an increasingly vulnerable one.

Sources

Bird, Keith W. Erich Raeder: Admiral of the Third Reich. Annapolis, Md: Naval Institute Press, 2006.

Militärgeschichtliches Forschungsamt. Germany and the Second World War. widening of the conflict into a World War and the shift of the initiative 1941-1943. Clarendon: Oxford University Press, 2001.