At the time of the Argentinian invasion, the UK was in the process of selling its aircraft carrier and reducing its naval capacity. If Argentina had waited a short time, it would have been much harder — if not impossible — for the UK to quickly put a task force together.
So, why didn't Argentina wait? Were there internal political, or other factors that caused Argentina to move when she did?
Background on sale of HMS_Invincible (from wikipedia) (see wikipedia for references to news papers reports etc.)
On 25 February 1982, after several months of negotiations, the Australian government announced that it had agreed to buy Invincible for £175 million as a replacement, under the name HMAS Australia, for the Royal Australian Navy's HMAS Melbourne. The sale was confirmed by the Ministry of Defence.
Background on decommission plans for HMS_Hermes (from wikipedia) (see wikipedia for references to news papers reports etc.)
Hermes was due to be decommissioned in 1982 after a 1981 defence review (that would have made the Royal Navy considerably smaller) by the British government, but when the Falklands War broke out, she was made the flagship of the British forces, setting sail for the South Atlantic just three days after the Argentine invasion of the Falkland Islands.
Note at present the UK has no fixed-winged aircraft carriers. If the Falklands was invaded today...
However, the Falklands have a lot more defenses, so they would be a lot harder to invade.