That's exactly what I was told about the huge Eucs in the Dandenongs by a local nursery owner. That when they get big and old enough they have a tendency to topple over because they have shallow root systems.

Eucs are self-pruning trees, and commonly referred to here as "widow-makers". Campers are advised to never pitch tents under large eucs for just this reason. Those and of course the notorious drop-bears...

Hhhhhmmmm. True that most of the time, a big tree isn't merely "meant" to fall over. Past a certain point, of course, something will happen to it, as all known trees of the earth are of a finite age ;-). But I'm not the only one to have been given this cautionary note about them: Eucalyptus Root System – Learn About Eucalyptus Shallow Root Dangers And More

The article discussed possible reasons that particular tree fell over: recent heavy rains in CA. But maybe the tree had been watered for many years if it was in a public park, thus forming an under-sized root system; then watering had been withdrawn due to CA's drought? There's a lot we don't yet know about that particular tree. As for what I said: I just repeated what a local nursery owner - who told me his family had been involved in farming in the Dandenongs for over 100 years - said about the stunning, huge E. regnans I'd seen there. He was striking a cautionary note to my hosannas of praise for the place being a paradise. For example, he also mentioned they'd had terrible brushfires a few years earlier. And that at times, the Olinda Rhododendron collection surely had to be watered to keep it from dying. Even though it's typically a very lush, rainy place compared to AU as a whole.

Feel free to ask him yourself: very friendly guy like most Australians! http://www.paddysplants.com/

Talk about literally "crashing" a wedding.

I am going to be transplanting an E. Gunnii in front of my driveway, but we don't have the "drop-bears" LOL. I doubt it will ever get large enough to cause a problem.

Eucalypts do drop branches a lot, especially in summer when they take up a lot of water and the branches become heavy. That's why they don't advise pitching a tent under one.

Transplanting of the cider gum not likely to be successful.

Fair use:

"Did the eucalyptus that fell Saturday fit the typical profile?

Yes.
According to a 2014 report from The Britton Fund, a nonprofit entity
from the International Society of Arboriculture’s Western Chapter, the
average age and size of failing eucalyptus in California is 65 years old
and 81 feet tall.

Saturday’s tree was an 80-foot-tall eucalyptus
that was at least 50 years old and had a trunk diameter between 6 and 8
feet, Los Angeles County firefighters said.

Two-thirds of trees
that failed were in high-use areas like Penn Park’s eucalyptus"

Causes can basically be soil fails to hold the tree, or trunk and roots are decayed, or both:

"Sometimes only part of the roots are compromised and others are not, further muddying the investigation for arborists, he said."

Expert: Doubtful that drought felled eucalyptus tree at Whittier wedding party - LA Times

Personally I think the problem here is related to what the link I posted above discussed...the tree is in an irrigated park and didn't form more than a surface root system.