For two reasons.
1)There is no situation, aside from the Sacraments, where God would "automatically" do a miracle. Your reasoning suggests that, in all the situations I mentionned, God would do a miracle to save them. Of course what you said is possible. But it is not necessary.
Wouldn't it mean that the DRPK has the power to make God do miracles to save the persecuted Christians, if they persecute them harshly enough? In the same instance, it would mean that the Jews have the power to make the fake Messiah come, by making events look similar. I do not think this makes sense.
2)God is Justice itself. The rules for salvation must be fair and give everyone willing a chance. It doesn't matter that most of humanity goes to hell, the problem is : are the rules just? To me, it does not seem just that a catechumen martyr would go to hell.
That isn't a rule that God would put in place, because God is Justice and because He cannot contradict Himself.
Sorry but I don't know what DRPK means.
1) If it took a miracle, then yes, God would provide a miracle. What you're missing is that no matter who gets baptized into the Catholic Church, whether it be you, me, the infant of good Catholic parents who scheduled it two weeks prior, the catechumen about to die or be martyred, the North Korean who desires it, or via a miracle, all are baptized into the Church via the same providence of God. The only reason that God does not succeed in getting others into the Church must be found in the reluctant will of those who do not enter it.
2) It is not God's fault, or His lack of attention, or any injustice on God's part that the majority end up in hell. He set the rules one time for all time for everyone and provides everything needed to live by His rules, and He judges all by those rules without difference or discrimination. This is the justice of God. There is no one about to die who sincerely desires the sacrament that will not receive the sacrament. How He accomplishes this is up to Him. Always was, is and will be for us all, no matter the circuмstances.
"The idea that someone died before he was able to receive Baptism, suggests that God was unable to control events, so as to give the person time to enter the Church. If time made any difference, God could and would keep any person on earth a hundred, or a thousand, or ten thousand years."