In dealing with the problem of evil we have to admit that we simply don’t know all the reasons why God allows evil to take place in every circumstance. To know that we would have to be God. And as I have said before I’m not God. God does however reveal to us in the Bible one reason why He allows evil in the world.

Romans 9
What if God, desiring to show His wrath and make known His power, has endured with much patience vessels of wrath prepared for destruction, in order to make known the riches of His glory for vessels of mercy, which He has prepared beforehand for glory.

As Piper has pointed out in quoting Johnathan Edwards:

You see, God doesn’t delight in evil for the sake of evil. Evil comes to pass that good may come of it. What good? And how does the existence of evil serve this good end?

Jonathan Edwards:

It is a proper and excellent thing for infinite glory to shine forth; and for the same reason, it is proper that the shining forth of God’s glory should be complete; that is, all the parts of His glory should shine forth, that every beauty should be proportionably effulgent, that the beholder may have a proper notion of God. It is not proper that one glory should be exceedingly manifested, and another not at all…Thus it is necessary, that God’s aweful majesty, His authority and dreadful greatness, justice, and holiness, should be manifested. But this could not be, unless sin and punishment had been decreed; so that the shining forth of God’s glory would be very imperfect, both because these parts of divine glory would not shine forth as the others do, and also the glory of His goodness, love, and holiness would be faint without them; nay, they could scarcely shine forth at all. If it were not right that God should< permit and punish sin, there could be no manifestation of God’s holiness in hatred of sin, or in showing any preference, in His providence, of godliness before it. There would be no manifestation of God’s grace or true goodness, if there was no sin to be pardoned, no misery to be saved from. How much happiness soever He bestowed, His goodness would not be so much prized and admired….So evil is necessary, in order to the highest happiness of the creature, and the completeness of that communication of God, for which He made the world; because the creature’s happiness consists in the knowledge of God, and the sense of His love. And if the knowledge of Him be imperfect, the happiness of the creature must be proportionably imperfect.

Is God less glorious because He allowed that evil be? The answer is no. God is more glorious.