What scale?
You need move 100 or so people a few hundred miles, in 48 hours.
The stadia are already there, the pitches are already marked and posts already erected, the medical suites are already present and fully kitted out, ALL the infrastructure is already there, fans aren't needed when playing behind closed doors; you just need to move 46 players, 3 officials and a couple of team doctors and half a dozen physios. Everything else is window dressing.
Yes, it would be nice to have the rest of the squads; yes it would be nice to have the nutritionists; yes it would be nice to have the camera crews and the TMO van. However, it's perfectly possible to play international rugby without any of those things - and far, far better to do so, than to not play any rugby at all.
If you don't have fans, then you don't need stewards, or policing, or any of the other stuff that makes these events large in scale.