When I was in the outback of Australia, I saw some awesome Toyota Troopies, and I can see myself doing an expedition in one of them. My first Toyota was an FJ-40 - one of the first in the USA before Toyotas were "cool". I still regret selling that vehicle after ten years of ownership. I drove it from Kentucky to Panama through Mexico and Central America. We had to search through five southern states to locate a new one that was for sale. When I got it, it took months to get spare parts for the trip. I was almost to the Mexican border before I could even locate a spare fan belt. Things have changed, and it's a very different world.The book 'What the hell are we doing here' goes into more detail than the videos above re. vehicle choice. The book is available on the kindle.
In the 1990's Toyota Land Cruiser spares, overland expedition kit and general knowledge was very limited. There were only a few companies provided expedition kit, and most of it was geared for Land Rovers. There was one manufacture for rooftop tents and expedition roof racks... now there are 50+ vendors selling the kit.
It made perfect sense for the team to use Defenders in those days. Kitting a vehicle now in the UK offers far more choice and equipment variety.