Tramticket, on 2018-December-02, 03:56, said:
You know that West has diamonds. West's diamonds might be AJTXX. 2D doubled could be very expensive if IMPs - do you really want to compete for a risky part-score? But strengthen the suit quality (give yourself the J as well) and it becomes more reasonable.
Come on. For one thing, West might pass with AJTxx. For another, on a more typical layout, West has AJx, and you contribute 2-3 tricks on defense versus 1NT, versus 7-8 tricks when declaring 2♦. Bidding 2♦ seems obvious to me.