Why cant triangle have more than one obtuse angle?

Because all the of the angles of a triangle add up to 180. If you have two angles that are greater than 90, then you're over 180 and don't have room to fit another angle in. 3 interior angles of a triangle add up to 180 degrees and the sum of 2 obtuse angles would be over 180 degrees.

A triangle cannot have more than one obtuse angle because if it did, then it would have to be a quadrilateral. For example, go ahead and draw a triangle with two obtuse angles. You can't do it, right? It's because you aren't supposed to, it will only make it a quadrilateral.