Blitzcrank's ult vs Galio's ult

So I was in a game as Galio, and my ultimate was cancelled by Blitzcrank's ultimate, how is that possible?

If Galio ulted first, Blitzcrank would have been taunted and couldn't use his ult, and Galio would have been silenced if Blitzcrank did ult first.

Is this because of cast times? (like how Tristana can still jump away after being rooted?)