My daughter was surprised when she came home and saw some new bookcases and a wardrobe in her bedroom. “Wow! How did you do this?!” She couldn’t quite get the hours of reading instructions, hammering, using tools and moving things to get it all in place.
It’s a little the same in academia I think. I remember being amazed at conferences that everyone else in the audience would be nodding along to talks. I could barely understand the ideas.
How are they getting all this? Why am I not getting it? How did that person talking figure this out?
At that early stage in my PhD I hadn’t had time to do the “invisible work” that could help me to understand. The background reading, the practice, the skill building, all the hours that go in to getting good at something.
Once you are good at something, it’s easy to forget about all that time you’ve invested, and simply focus on the end result. For passing the viva it’s essential to try to hold on to that awareness of time spent. Hold on to the understanding that you have invested all of that time and focus into work that has produced a good thesis and a good candidate.
You got this far because you did the work, even if everyone else sees only the end result.