OP, not sure why you are convinced this is something that happens only to naturals. Splits happen to everyone. As soon as you trim they start to happen at a microscopic scale and depending on how long you wait to dust, they can grow to a size that causes you problems.
There are naturals who don't have problems with splits and don't need to trim often. These are usually people with thick strands (eg @
ms-gg). Then there are those like me who dust them before they happen. And I know you say you trimmed a month ago, but how long before that did you trim? You can't leave hair undusted for months then do a trim and be 100% sure you got rid of all the damage, especially if your trim was about an inch or so. Not sure what made you trim, but if your ends were looking thin, then the splits might have extended beyond where your trimmed...so you may have left frayed ends behind which continue the damage.
I once posted a magnified image of my hair to show you an end that wasn't split but it was what was left after a split had torn off, hence the reason it's pointed.
It was less than a millimeter long (because that's my thumb nail you see). But because I dust every 8 weeks, and dust about 1/4 of an inch or so, I usually cut off about 5 mm AT LEAST so I guess I do a good job of ridding my hair of those dangerous ends.
So yeah, all hair splits. How fast this happens depends on how fine the strands are. How much this will cost you retention depends on how long you allow the splits to stay in your hair and grow. The more frequently you dust, the more you're likely to keep them from being a nuisance. But remember if you're only starting to dust now, it may take many months before you start to reap the fruits of this good practice, because as I've said before, your trim may be at C which leaves problems.
Cutting at A is better, but even then, you can see some of what's to the left of that is damaged. So it may take a few more big cuts to get to the point where your cut leaves whole ends that have a long way before they get ugly. And THEN you can start the prevention program of regular dusting instead of a repair program of big trims.