I always thought it was something to do with sonar used by boats effecting their navigation?
Seems there’s a few theories though and it may depend on the situation as to the cause. For example their were beachings hundreds of years before electricity was even invented. Here’s a short summary, http://en.wikipedia.org/wiki/Whale_beaching
Speaking of Tasmania and dead animals, last time I was there we were driving back to our accomodation after watching the spectacle of hundreds of birds coming in from the sea to roost in the sand dunes at dusk. In that hour we had to slow down/stop over a dozen times to avoid killing wallabies on the road. If you go for a drive along any tasmanian road away from the cities in the morning, you’ll see many many carcasses. Normally Tasmanian Devils cleaned up the kills very effectively, however their numbers are dropping (from facial tumour disease) and so the bodies are piling up more today than in the past. From a rewilding perspective, you could get more meat than you could ever possibly eat, although spoilage from the guts is always a risk with roadkill?