The siege tactic is employed because they are trying something so hard it has never been done before, and even with all that support, years of planning, decades

The siege tactic is employed because they are trying something so hard it has never been done before, and even with all that support, years of planning, decades of training, and months on the route, two of the best climbers in the world barely managed it. If these 2 guys were alone ... they would have faced a significantly greater obstacle Exactly. They, world-famous world-class climbers, wouldn't have even been able to complete it. You can look at it like, they are advancing the "state of the art" of climbing. If you try I am sure you can think of parallels in engineering, where something never-before is achieved in the face of absurd difficulty, opening the doors to future engineers.