Grant did not "bumble". His intent was clearly stated, to engage Lee and the ANV and prevent any possibility of reinforcement being sent to oppose Sherman's campaign, and to deplete Lee's forces and supplies till he could no longer field an effective force.
As for Cold Harbor, as terrible as it was, it has been overblown by many, the total KIA was 1,905, wounded were 10,570, the result of the victory was that Lee still had to fall back. (total casualties=14,931)
Let's compare Cold Harbor to Stone's River, total Union loss (KIA, MIA and wounded) 11,575. CSA losses 25,560.
Or Nashville? Union's total loss= 2,140. CSA=15,000.
Or Ft. Donelson? Union loss= 2,231. CSA= 15,067.
Or Pea Ridge? USA losses= 1,349. CSA=5,210.
Or Vicksburg? USA losses= 4,536. CSA= 31,277.
But all we ever hear about is the huge losses at Cold Harbor, and how cold hearted Grant was, he was such a butcher blah blah blah...So if he was all those things, what were the CSA leaders that continued to fight a war that they knew was lost in 1863?