Viva candidates pretty much have all the answers. That’s not because the viva is easy or the questions are predictable or because candidates can somehow prepare for every possibility. The viva’s not a quiz game.
Some questions in the viva might be trivial in the sense that they are easy for you to answer. The fact that something seems easy to you doesn’t diminish it in any way.
The viva generally is non-trivial. It’s not a game. Any ease you might feel with questions is down to your hard-earned talent.