I don't think it is a "thing" for dogs to find caves, she is the only one I know of!
I got into caving in 2010, and joined a Cave/Cliff/High Angle Search and Rescue team in 2012.
One of the earlier caving trips I did was in the UK, and there was a young 6mo old Aussie being trained for wilderness SAR I met. That prettymuch sparked my love of Aussies and the idea of using dogs for Search and Rescue.
I couldn't have a dog though. My life and housing was not right for one.
In 2013 that changed, and I started searching for a breeder, and got Edraith in 2014 for the purpose of training her in Search and Rescue (her name means "Rescue" in Elvish). Wilderness, not cave rescue (we are NASAR airscent certified), although she hangs out with our Cave unit (literally, sometimes, we do train in a dog life safety harness). Basically, I am on two teams - one is K9 and one is Cave.
We hike a lot, and she has been underground. With the SAR training, I am used to reading her body langauge. I also know what her body language looks like when she gets excited to go underground. So one day when we were out ridgewalking (looking for new caves) and she was along. Caves have a unique ecosystem and have a distinct odor (likely due to the different soil / moisture / bacteria types - the odor varies by region, I can notice it so I am sure a dog can!). She stuck her nose to the ground - mind you no surface indication of a cave - and started showing me that "underground excitement" body language. I went over to check, and as you see in the video it's a barely noticeable spot in the leaves that is blowing out air. This is good news for cavers - pressure and temperature differences make caves "breathe" - and the more air movement, the larger the void underneath. Dug it open, down five pitches and a depth of over 350ft down and bam...

Rest is history!
She has found a few other caves as well, but none so impressive as that one.
Basically I never specifically trained her to find caves, it is just a combo of what we do, she put two and two together when she recognized the scent, and I noticed and responded to what she was telling me because we have a partnership that I think is a little unique to SAR dogs. In more than any other "sport", the human is really just along for the ride and it's a matter of listening to your dog, rather than your dog listening to you.
Here is the whole video of the first day that I took - shows the hole a little better:
This is what we got into:
serenity valley by
Amata Hinkle, on Flickr