Well, at the quantum level, science is only concerned with probabilities and not predictability. It’s impossible (as far as we know now) to predict anything exactly at that scale.
At our scale, though, most everything that scientists are concerned about is predictable. Gravity doesn’t act randomly, electromagnetism doesn’t act randomly, the chemical properties of matter are not random, genetics are not random, etc. Now, when you combine some of those fundamentals into a system that is complex enough, you will see the appearance of randomness emerge, but it isn’t truly random, it’s just an artifact of the complexity of the system. That’s what they came up with chaos theory to account for.
If we could construct perfect models of complex systems at the macro scale, we should see there is no real randomness, but we simply can’t do that mathematically for most systems because we can’t solve the equations.
Politics is at a quantum level.
A mad man shoots an archduke.
A Tommy decides not to shoot a Kraut he has in his sights, eye to eye not 15 feet apart...