Yep, can’t means didn’t but in the present tense.
If you didn’t do something, it means that at the time that you might have done it, you actually couldn’t do it.
Many people will argue with this, aggressively and even violently. But I’ve yet to see anyone who can offer any real, logical evidence to the contrary, while reality offers pretty much total evidence supporting this.
Why didn’t I do X? Because, given all the factors of the situation, I couldn’t do X. Though I might well have done it and/or do it at another point in time, in another (possibly even very similar) situation…