People think "who designed the designer" is a knockout, but it only applies to contingent things. A clock needs a clockmaker because it's a complex arrangement of parts that could have been otherwise. God, by definition, is a necessary being—not a complex part needing assembly. The question asks for a cause of something that is the ultimate cause. Meanwhile, a multiverse doesn't answer fine-tuning; it just multiplies the machinery that itself needs explaining. You're not solving the puzzle, just pushing it to a higher shelf. The design inference stands: tuned complexity points to a mind, and a necessary mind doesn't need a designer.