This is all a matter of opinion, but I don’t necessarily believe in “fate” myself, or that events are predetermined as such.
Probability is certainly a factor, but I think in magic we should discard probability and focus on possibility. Take a look at things like Littlewood’s law, or the block world concept:
With the idea being that creation is finished, and we exist moment by moment at the crossroad of all possibilities and every possible outcome, it’s only our consciousness (the present moment) which slides around through all the intersecting paths of time.
With that said, it’s anyone’s guess why certain rituals work and others do not.
Again, completely my personal opinion, but I understand the mechanism by which magic works to be that (by ritual, petition, or whatever means), you impress a desired state or result into your subconscious, which then works to manifest that state or result into your perception of reality.
Your conscious mind is capable of undoing said work through doubt or obsession (lust for results) – “A man is what he thinks about all day” – which is why the advice given is to avoid lust for results by not thinking about the ritual, or if you do think about the situation, to simply feel gratitude and acknowledge that it is done.
There seems to be something intrinsic to love magic that ties up all our thoughts about the other person. I would say many people, even those who have other options, a strong concept of self, etc., still fall prey to doubt/obsession when it comes to lovers, perhaps because it’s difficult not to experience rejection from someone you were or wish to be intimate with, emotionally and/or physically, as a commentary on who you are as a person, and that can pierce right into your subconscious and affect how you think of yourself.
If there are conflicting values in your subconscious, even ones you aren’t aware of, then the most likely outcome is that things stay exactly as they are (e.g. you remain single). Alternatively, reality bends around you in line with whichever subconscious belief currently has the most footing, but as your mind vacillates between different beliefs, you get partial or impermanent manifestations, or you see results only to have them followed by setbacks.
There’s likely a bit more to it than that, but that’s how I see it.
With the above in mind… if your subconscious was sufficiently impressed with the kind of relationship you want, this could in some ways explain your outcome.
Also, depending on the timeline, you could still find your ex will come back to you seeking reconciliation at some point in future… at which point you could very well have lost interest in him.