Frequently in my practice the question arises on what other people's motivations are, and my clients often ponder way too much on what "made" their partner, parent, boss, colleague, act the way they did.
That pondering usually involves a vigorous work-out of their peanut.
Yet the answer to the question "why does a person do what they do" in most cases involves that other person's emotional world, and not something you said or did to them.
So the endless questioning of "but why do they do that?" will very often not have an answer that pertains to your behaviour.
An example:
You have a string of great dates with a man, over several weeks/months, and suddenly, out of the blue, he stops returning your calls. Unless you have smacked him in the face, literally or metaphorically, during your last date, it is unlikely that his "ghosting" you has anything to do with you, but rather comes from his getting cold feet, or having met someone else, or whatever his reasons are - "his" in that they pertain to him, and not to you.
Another, more straight-forward one:
Your husband beats you up (physically or emotionally). You keep questioning yourself what you have done wrong, to deserve such a treatment. The answer is nothing. Nothing you can do makes you deserving of domestic abuse.
By all means, do look into your conscience to see if you have done anything wrong; but if you can't find anything, try the explanation that it is their stuff, their baggage, and has not much to do with you. And once you can see what is their stuff, you can let it go, and work on your own.
Now why would I discourage anyone from spending too much questioning another's motives?
Because in a way, as long as you keep wondering, possibly looking for explanations/excuses for the other's behaviour, it prevents you from asking yourself the real question (and to draw conclusions from the answer): "is that behaviour acceptable?" and its corollary "why do I put up with it?".
It may just be more useful to spend time understanding what is said rather than thinking about why it is said.