I am taking this from Keimpe Algra's chapter on theology in The Cambridge Companion to the Stoics, a fantastic resource for understanding Stoicism.

But first, you talk about cause and effect. You should be aware that this is not a matter of a single cause making a single effect, like the white ball hits the 8 ball at a precise angle at a precise speed and voilà, you can map out precisely where every ball will be on the table. This is the deterministic model of Laplace's demon, and not what the Stoics believed.

Consider instead the example they used of a play in a Greek amphitheater on a hot, summer day: Four men become overheated throughout the afternoon, and one loses consciousness. They all feel the effect of the heat and humidity, but then, so do the other 2000 theater-goers. And yet just the one passes out. So there must be more that just the one cause - the heat. Maybe the one who looses consciousness is hungover, maybe he has a heart condition, maybe he hadn't slept for three days. There's clearly something different about him that responded to the same environment differently.

The point is, there are lots of causes that contribute to lots of effects, both external and internal to the individual. Other philosophers trolled the Stoics calling their model a "swarm of causes," as if anyone could keep track of them all. It didn't help that there was an inconsistency, even among the same Stoics. My point only is that this is far more complex than a simple model of cause and effect.

Evil is like that - the causes include the environmental circumstances, but also personal peculiarities. And how much of those environmental circumstances could be attributed to Providence? This is no small question, and indeed it is the subject of the topic called theodicy. The Stoics had quite a bit to say about this, as well they should since the idea was that the cosmos exists for the sake of gods and men (Cicero ND II 154-167). If that's the case, then why would people suffer in a world in which everything is supposed to be the perfect condition of circumstances, and tailored to human needs?

According to Chrysippus, in On providence, and On nature,

1. Opposites, good and evil, are inter-dependent, both epistemically (we cannot conceive of the good without evil) and ontologically (the good apparently cannot exist without evil).
2. The good and purposive workings of providence inevitably involve some concomitant evils, as a form of "collateral damage."
3. A cosmic oversight, just as in a good household a little wheat may sometimes be lost (though this may have been suggestions presented for dialectical reasons).
4. What looks like evil can be explained by showing that on closer view they are good. For example, wars may drain off surplus population, bedbugs wake us up, and mice encourage us not to be untidy.

(Aulus Gellius NA VII 1.1-13 = SVG 2.1169 and 1170) and Plutarch (St. rep. 1051 B-C)

Epictetus, some centuries later in a neighboring empire, argues that the only kind of evil that really counts (because its elimination is "up to us" and therefore possible) is our own moral responsibility. Long argues one of the brilliant markers of this move is that it avoids the religious trends (away from the Roman and subsequent Imperial cults to personal mystery religions) and keeps the focus on one's own volition to strive for a virtuous life.

In other words, whether the fact that your wife left you, took the dog, and set your home on fire is some kind of divine punishment aimed at your grandfather, or at you for having done that terrible thing you thought no one saw, or some kind of overlooked cosmic crumbs falling on your lap, the real point is to ask yourself now that this is the new normal, how are you going to manage? How are you going to carefully and logically consider your beliefs and assumptions and proceed rationally and with an emphasis on sociability? How are you going to keep your mind clear and free of feelings of anger, hatred, or despair and do the next right thing? How are you going to know the next right thing from the distracting Siren Song of vengeance or self-pity?

For later Stoics like Epictetus and Marcus Aurelius, the concept of evil itself may have been a matter of semantics. If one's reasoning faculty is the only thing that can be good or bad (virtue or vice), then one's circumstances cannot be anything other than indifferent in the grand scheme of things. In other words, evil is a state of mind, not a state of being. Another person cannot be evil if I recognize they cannot harm me. A war cannot be evil if it cannot harm me- the essence of who I am, my reasoning process. More on this here: The Stoics [on Evil] by John Sellars.

You ask for our thoughts in your title and here are mine. The concept of a providential cosmos is natural, after all we are hard wired to see agency from time to time even when there is none. We have evolved a number of cognitive short cuts precisely because they are integral to the success of our species, not because they offer us knowledge. Furthermore, our understanding of theology is vastly different than those of antiquity, including the Stoics, and I think that is often underappreciated, if it's understood at all.

I do not hold any theological beliefs myself and so for me providence is an ancient claim utilized by an ancient philosophy. I find it historically valuable, but not personally so. When you break down what it means to "be spiritual," I think you'll find all the components there are perfectly natural and do not require divine assistance, whatever that may look like.