The Elder Spell is a projectile (or at least interacts with the Windwall tech which Braum E uses like a projectile), so it can be intercepted and deal the effect to Braum instead. The effect is 'die' - technically it's 'lose all shields and take 100% current HP damage*', but that's pretty much the same thing.
* also checks for a few buffs you may have, but you had none of those in this clip
Considering the inconsistent interactions of Urgot's R and the Elder Spell (Urgot chains no longer attach to Braum when he intercepts them since 1 patch after the VGU release), I don't know which set of interactions would be the intended one - to die of Elder but not Urgot, to save from both or to die to both? u/Rovient is responsible for the Elder Dragon shenanigans, so perhaps he could comment on that.
For those curious, here's the initial patch interaction for Urgot R vs Braum...