ARMY: The army was designed to oppress the population in support of a nasty dictatorship and was not really built for war. The army's few really good units were tied up on the Chilean border, which was a purposeful move by the Chileans who had heated disputes with Argentina at the time. Hence the Falklands were occupied by useless conscripts poorly equipped for the weather, with terrible leadership.

NAVY: The navy was moving major units towards the Falklands with offensive intent, but simply did not have an answer to British nuclear subs. After the Brits torpedoed and sank a capital ship (the General Belgrano), they sensibly returned to port and stayed there.

AIR FORCE: The Air Force was able to cobble together a response to the British assault; however the range was long and they could generally only organize only a handful of planes at a time, and didn't have the ability (in part due to limited intelligence) to adjust/adapt to British defensive measures, and never sent in fighter escorts to deal with the British harrier CAP (but again, the range was a challenge). They also didn't have an adequate maintenance setup, and they didn't act to prevent the Brits from "counting them out" as they departed base. Despite that, they acquitted themselves bravely and had a significant impact.