There are millions of questions yes (well maybe.) but let's say that I choose...
David Beckham. Because fuck it.
Let's also say that the game knows about ... 5 million characters because why not lets make it a massive number. We'll also assume that for simplicities sake that the answers are evenly distributed (if it can only be yes or no then it halves the solution set, if there are 1000 sports then once it chooses the corect one it takes it down by three decimal places...) Both are unrealistic but good enough to make my point.
We start with 5 million characters
The first question is "Has your char really existed" (Is he/she fictional?) so I say yes.
Now there is 2.5 million.
Is my character a male? yes.
1.25 million.
Is my character american? (assuming there are roughly five choices at this point, which there probably isn't, it probably woul only ever start with american tbh)
No.
1 million choices now (see how it got rid of one fifth of the solutions even though it wasnt about my character?)
Is my character linked with video games (lets ignore this one)
I said dont know though.
Still one million choices, is my character swedish? No.
(Computer is looking through Non-American Male Non-fiction at this point, so it goes to european. If i say no to three european countries in a row id bet my left nut that it would try for a new continent)
Is my character english? yes. Lets say that the amount of famous non-americans who AREN'T british are 50% of the solution set, that seems fair to me. As britain is rather important and always has been. So now that it know, after 6 questions, that my character is a British Male who has existed but was linked with video games we are down to...
500,000 possible solutions (honestly im being very generous here it's probably less than that.)
Is my character black? (it starts going into personal details here because those are very apparent and not easy to say "i dont know" to) No. Ill cut 10% off the solution set (90% of famous brits are white? i dunno.)
450,000 (7 questions)
Is my character from youtube? Naw. But fuck that question idk about brits and their youtube habits.
Is your character linked with sports.
Yes. I'm saying thats worth a 66% cut because there are lots of famous white male brits who arent athletes. Or hell ill keep being nice to the linear thinking and say its only worth cutting down to 200,000 solutions (which is a GROSS over estimation)
Is he a soccer player?
Yes.
Well that cuts out the 9 brit atheletes who play otehr sports :p jkjk, but maybe 50,000 are cut out (this is where you cna start to see, well DUH, the most people would play football, being a brit athelete, so thats the question the former would link to)
150,000
Is he currently playing? No.
Let say that 10% of every brit footballer who has ever lived is playing right now. So That leaves us with 135,000
Is he a midfielder?
Yes.
NOW. At this point the game know that it should be looking under Male Brits Who Have Existed. And it can do a "Select from" statement to narrow down to just midfielders in soccer who are retired (or dead)
I dunno how many positions there are in soccer but i want to say 4, so now the solution set has a (very inflated) 35,000 (ish) solutions possible. BUt realistically, in that solution set i described, it's going "Ok we have X number of solutions left, but the percentage of people who have chosen answer A (David Beckham) is much higher than any other solution left over. So we will form questions based on this. So the next is;
Has he ever played for Manchester United.
Yes.
We are 12 questions in, and I dare you to come up with any Former-Manchester Midfielder more famous than David.
Im going to say "dont know" to the rest of the questions, because at this point even with the (2500?) other people to have played midfield for them. The game will default to the most likely answer...
and....
two questions later about his famous sons and being underwear model and some championship thing, it guesses david beckham.
Tl;Dr: Because the solution set decreases exponentially and it will (at a given point) default to asking questions to try and 100% verify the most likely answer in its little book o' answers. If it can't itll guess that anyway, and 99% of the time be right because people are pretty easy
You asked "Well how does it know which sport to guess?" because, if i know that the person is Brit, guess soccer then rugby, if he is american, football then hockey, etc, because those are the most likely.
Its the same reason it asked right away if he was american. More Characters for this game would be american than any other nationality.