Does the above explanation cover why the majority of fighter aircraft* (running water cooled engines) used the V-12?
*Not to mention the UK bombers using the Merlin V-12 series.
It does have something to do with it. Vibration in aircraft is a prelude to serious problems, because aluminum work hardens pretty quickly under vibration modes and this causes cracking and structural failure.
The more telling metric for our application under discussion (diesels in autos) is how many of the finest autos in the world use V-12’s. Think Ferrari, Lamborghini, Maybach, Jag, et al. Very, very smooth engines.
The original point was about diesels in cars. One of the knocks against diesels in the past (esp. I-4 diesels) is that they had more vibration vs. gas engines of the day. It certainly is possible to build a reasonably smooth I-4, but it is far easier to deliver a good diesel in I-6 and V-12 configurations, as is evidenced by how the Germans (who, after all, created and perfected the diesel engine) are using this configuration in high-end cars. The BMW 5-series uses a lot of I-6’s in both gasoline and diesels. Mercedes is using V-12’s in their highest-end autos.
The US auto manufactures are at a point where I’d like to tell them “OK, look, you’re past the point where you’re going to win back market share with innovation, because the US consumer has had 20 years of your ‘innovation’ and how it doesn’t pan out. So just copy the Japanese and Germans, do it cheaper and better and work at just surviving until you can get rid of the UAW liabilities and get back to being a car company instead of a HMO that makes cars.”