He chose to prioritize achievable objectives and present a Dwarf Realm to their foes that would kill for every Dwarf dead and every foot of Dwarf lands taken. He did what every King of every Karak under siege by enemies, cut off from allies, would have done.
That our actions took place does not diminish just how extraordinary in nature they are.
Oh, I don't dispute that, be we are humans and thus more likely to see to good side of things. I feel that Thorgrim might not feel so positive. Dwarves have been portrayed as much more likely to emphatize their failures or perceived failures.
I wouldn't be surprised if Thorgrim thought that K8P and now Karak Vlag are proofs that his whole approach was flawed and that someone else might have done better. And feel guily enough about it...