I had a few moments in life when I met a person that I used to see only on video. I wanted to say “on TV”, but that doesn’t fit the modern context. Who are these people? Musicians, speakers, engineers. Most of them are among best pros in their industry, so there’s a lot to learn from them.
I’m not looking forward to meet such people. I have no idea what I should ask them. Usually you have to be at a very advanced level of skill to be able to ask an interesting question. They most likely are very popular, so meeting a new person might be more of a uncomfortable burden rather than an interesting event, so I don’t want them to feel bad.
I think it’s totally fine if you don’t know what to ask a president when you meet them in real life.