In a large pot, bring 4 quarts water to a boil. Meanwhile, in a food processor, combine the bread, 1 garlic clove, 1 tablespoon of the parsley and ¼ teaspoon each salt and pepper. Drizzle in 2 tablespoons of the oil. Pulse until evenly moistened and broken down into a mixture of coarse bits and finer crumbs, 5 to 7 pulses. Transfer to a 12-inch skillet; cook over medium, stirring, until golden brown, about 5 minutes. Transfer to a plate; reserve the skillet.

Add the pasta and 1 tablespoon salt to the boiling water; cook, stirring occasionally, until just shy of al dente. Reserve 1 cup of the cooking water, then drain the pasta; set aside. In the skillet over medium, combine the remaining ¼ cup oil and remaining 2 garlic cloves. Cook, stirring, until the garlic is golden brown, about 2 minutes. Add the anchovies and cook, mashing them with a wooden spoon, until they have completely broken down, about 1 minute.

Remove and discard the garlic, then stir in the tomatoes and ¼ teaspoon each salt and pepper. Cook, uncovered and stirring, until the tomatoes have fully softened and the mixture is jammy, about 8 minutes. Add the pasta, olives and ½ cup of the reserved pasta water. Cook, stirring and tossing, until al dente, 2 to 3 minutes; if needed, add more pasta water 1 tablespoon at a time. Off heat, taste and season with salt and pepper. Serve sprinkled with the breadcrumbs and remaining 1 tablespoon parsley.