A lot of little things contributed to this I think.

1. Flavius is likely right. Most of their training would have been with towed targets with planes doing 150-250 mph. Moreover, Swordfish would have been a very small target. Operating according to the "drill" may have had them leading these small targets way too much.

2. While the optics on the Biz were excellent, I don't believe they had radar gunnery for any of the tertiary armament. Nor were visibility conditions good for gunnery. Dicey weather may be miserable for TO&L on a carrier, but was ideal for torpedo planes on the attack.

3. Simply didn't have the volume of fire that was necessary. The convoy battles to Malta and Archangelsk, along with Coral Sea and Midway, had yet to occur. Take a look at the amount of AA retrofitted to all of the battlewagons in 42-44 as evidence. Biz mounted 76 AA-class tubes, only 16 of which were in the near 40mm range. Most were 20mm, though 16 were 105s in double mounts. These were good weapons with high angle mounts. Oddly, Biz did not mount the proven 88mm AA weapon so ubiquitous in most of the rest of the German armed forces.

By contrast, the New Jersey mounted 129 AA tubes, 80 of which were 40mm. This was in addition to the 5" DP secondaries. Kongo was retrofitted to mount 118 25mm guns plus here DP tertiaries.

4. Altitude fuses. They could do altitude fuses to blow up at a set altitude, contact fuses, or timed fuses. The Germans did NOT have the proximity fuse just then being developed (and which was VITAL to late war naval AA effectiveness.