The point is he's won less than half of the available thus far, and he's unlikely to improve that pace in the future. He's going to do well in New York and the other states on the east Coast, but he's also going to do relatively poorly everywhere else (getting 30-40%, which not enough to get 51% of the delegates in most states), especially on the west coast.
Incidentally, Trump plateaued nationally, and he's down about 6-8% from his peak last month.