Remember that an obtuse angle measures greater than 90°.
A triangle never contains two obtuse angles.
If a triangle were to contain two obtuse angles, then there would be two angles in the triangle that measure greater than 90°, so the sum of these two angles would be greater than 180°. Since we know that the sum of all three angles in a triangle must be exactly 180°, it doesn't make sense that the sum of two of the angles would already by greater than 180°.