He never 'had' it to begin with. MacArthur was an utter embarrassment to the US. He started out in public relations, and much of the reason he narrowly avoided getting sacked on two occasions prior to 1943 was because he was exceptionally talented at shifting blame from himself onto others. At times he could appear completely insensitive to danger, yet he shrank away from visiting troops serving under him in the field, especially the sick and wounded. He had a habit of becoming ill at times of crisis, and his behaviour even when he was young (remember that by 1941 he was 60) included a tendency to hyperventilate and vomit.Jack the Potato said:
His closest group of 'advisers' weren't really advisors at all. He kept them like a pep group, constantly encouraging him and insisting his decisions were sound, plus a personal physician he kept close by at all times. He never waivered his meal and rest schedules, and many of his decisions put his own and other nation's forces under far greater risk than they would otherwise have had.
For example, nine full hours after the Pacific war had got into swing, Luzon's Army Air Force squadrons of 107 P-40s and 35 B-17s hadn't moved- neither retreating south to more secure air bases, or striking north at Japanese front line airfields on Formosa, because MacArthur couldn't make up his mind quite what do do with them. The Japanese flew in and solved his dilemma by wiping out planes and ground staff alike, ending any American ability to mount an air defence.
The Army-Approved plan Orange-3 recommended retreating to the Bataan peninsula and mounting a concentrated defence from there. Rejecting it as defeatist, MacArthur cancelled any buildup of food, ammunition and medical supplies around Manila. Bataan saw through the entirety of December 1941 without any measures taken to organise its defence.
Once the US and Philippino forces were forced onto Bataan anyway, they were woefully underequipped for an extended fight. The Japanese considered the US plight so hopeless that they removed an entire Division to go fight in the Dutch East Indies. This left the remaining troop ratio in the region of 2:1 in the American's favour, and while MacArthur and his staff effectively locked themselves in Malinta Tunnel on Corregidor island at Bataan's southern tip, only visiting Bataan once -notably avoiding any of his own troops- Jonathan Wainwright put up a furious and valiant fight against the Japanese on the Peninsula itself, critically low on ammo, reduced to half -and later quarter- rations, and with nothing to fight the widespread Malaria sweeping through the ranks.
Meanwhile, back on Corregidor, MacArthur did his best- sending pleas to Washinton for reinforcements, which included all manner of threats and charges. Simultaneously he pumped out press communiques misrepresenting the plight of the Allied troops, the enemy strength, and his own role in the whole affair. MacArthur was determined not to sink with his own ship. He diverted much of the remaining food supplies to Corregidor and was so determined to hole up there with all the supplies he could hoard that it took a direct presidential order to force him to retreat to Australia, leaving Wainwright in charge of rapidly diminishing forces on Bataan.
All this only gets us as far as March 1942, and it doesn't get any better. Between his men-wasting greed for a quick victory for the papers at New Guinea, to his abhorrent practice of labelling all joint-Allied victories as American, and American defeats as Allied, he was a theatrical schemer who was quite rightly described by contemporaries as "The greatest Actor to serve in the U.S. Army."
In short, he was terrible.
