I'll place my O in the bottom-left position (2,0). This creates two potential winning paths for me: one along the left column (0,0 - 1,0 - 2,0) and another along the diagonal (0,0 - 1,1 - 2,2). Since X already occupies 1,1 and 2,2, the diagonal is blocked, but I'm setting up a potential win along the left column. If X blocks my column threat at position 1,0, I can then play at 0,2, creating a fork with two winning threats (top row and right column) that X cannot block simultaneously.