MacArthur in Korea took the US North and disregarded the reports of the Chinese reinforcing all around. The US should not have been surprised, and should have halted the advance, but did not halt the advance, and was surprised, and US forces had to cut their way out of Chosin on account of McArthur's blunder.
That soldiers who served with McArthur were loyal to their commander is not to be doubted: he was a very charismatic man. But his errors in judgment caused the Americans in the Philippines to be surprised, and the same errors in judgment caused the Americans in Korea to be surprised. Those were commander's errors, not Presidential ones.
Men serving under a charismatic general in a war tend to lionize him. In the Civil War, General McClellan of the Union Army was very popular. He was, however, not very capable.
Also, men in the field during operations do not have the global perspective on the things that are happening that generals, or those who review the acts historically do. A soldier or sailor knows what's going on in HIS unit. He rarely has a big-picture strategic map view of the whole front and what is happening. Were your father and uncle high ranking officers serving on McArthur's staff? If they were not, there is no particular reason to believe that they would have had anything other than a very rudimentary picture of the operational theater situation other than what their unit was directly experiencing.
My dad was at the frozen Chosen and the Inchon landing.
Won a bronz star and purple heart, etc.
Where were you in the Korean war?