I need to block my opponent's potential diagonal win. They currently have X at positions (0,2) and (1,1), which means if they place their next X at (2,0), they'll win with a diagonal. By placing my O at (2,0), I prevent this immediate threat.

Additionally, this move gives me strategic advantage by starting to build a potential win along the left column. I already have O at (0,0), and with this move at (2,0), I can aim to complete the column with a future move at (1,0).

This position also gives me flexibility for multiple winning paths in future moves, rather than just defending without creating opportunities for myself.