Before you toss the coin, God has determined with full certainty on which side it will land based on everything riding on that coin toss and all the third-order consequences, in His infinite wisdom. It cannot land on any side other than the preordained. The way you find God's will is to flip the coin.
To the pre-statistical brain it was unthinkable (and probably blasphemeous) to perform any sort of expected value calculation on this.
We know today that the frequency is useful for making decisions around the individual throws. Back then, that connection just wasn't there. Each throw was considered its own unique event.
(We can still see this in e.g. statistically illiterate fans of football. Penalty kicks are a relatively stable random process -- basically a weighted coin toss. Yet you'll see fans claim each penalty kick is a unique event completely disconnected from the long-run frequency.)
Statistics is a very young invention. As far as we know, it didn't exist in meaningful form anywhere on Earth until the 1600s. (However, if it existed in the Americas earlier than that, that would explain why it suddenly popped up in Europe in the 1600s...)
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Important edit: What I know about this comes mostly from Weisberg's Willful Ignorance as well as A World of Chance by Brenner, Brenner, and Brown. These authors' research is based mostly on European written sources, meaning the emphasis is on how Europeans used to think about this.
It's possible different conceptualisations of probability existed elsewhere. It's possible even fully-fledged statistical reasoning existed, although it seems unlikely because it is the sort of thing that relies heavily on written records, and those would come up in research. But it's possible! That's what I meant by the last parenthetical – maybe Europeans didn't invent it at all, but were merely inspired by existing American practice.
It's pretty common, for example, to believe that God is on our side and we will win the war or somesuch. Actually walking onto a battlefield with a literal expectation of divine intervention... much less as common. Pious generals still believe in tactics, steel and suchlike. Not always... but usually.
European pre-modern writers were mostly very pious. The works preserved are likewise very pious. Greek philosophers were often closer to atheists than later Christians.
> It's possible different conceptualisations of probability existed elsewhere.
Rudimentary sampling theory 100% predates 17th century Europe: https://ckraju.net/wordpress_F/?p=55
The general insight is that complex counting would force some kind of Bayesian or probabilistic reasoning even one that is informal, intuitive, rudimentary or partly incorrect. Whereas a theory of divining stones usage would have very little actual complex counting involved, maybe they had the tribal equivalent of fortune slips, and so they would not be cognitively challenged to reason about dice. What constitutes complex counting, I don't know, ask the researcher. But IMO it's not out realm of impossibility and time and again we have discovered the old ones of Homo sapiens were more cognitively/intellectually sophisticated than these kinds of scientists assumed earlier. I'm not wedded to this, it would be hard to prove, especially as a hypothesis involving human cognitive constraints/evolution, but I won't dismiss it as completely implausible either. It is an interesting if-then "archaeological cognitive science" argument, that's all.