Short answers, pulled from the story.
American aviators gave it that nickname because Japanese aircraft losses were so disproportionate. During a post-battle debriefing, a U.S. pilot described the experience as 'just like an old-time turkey shoot down home.' Japanese losses exceeded 350 aircraft on the first day alone, against about 30 American aircraft lost.
When Admiral Koga died in a plane crash on the 31st of March 1944, his chief of staff was carrying the Z Plan documents in a briefcase. Filipino guerillas recovered the briefcase from the wreck and transported the documents to MacArthur's Military Intelligence Service in Brisbane. The translated plans were forwarded to Admiral Nimitz and reached fleet commanders before the battle.
Both were sunk by American submarines. USS Albacore torpedoed Taihō on the morning of the 19th of June; vapors from ruptured fuel tanks were accidentally spread throughout the ship by poor damage control, and a spark triggered catastrophic explosions around 14:30. USS Cavalla struck Shōkaku with three torpedoes around noon; fires ignited refueling aircraft and exploding ammunition, leading to a vapor explosion that sank her north of the island of Yap.
Many officers, especially aviators, believed Spruance was too cautious. By refusing to move Task Force 58 westward overnight on the 18th of June, he denied his forces the chance to close the range and potentially destroy the entire Japanese Mobile Fleet at dawn. Admiral John Towers demanded Spruance be relieved, though Nimitz refused. Spruance's defenders pointed to his orders, which made protecting the Saipan invasion fleet the primary objective.
They struck the Japanese fleet just before sunset at extreme range, then flew back in darkness with nearly empty fuel tanks. Of the 226 aircraft launched, 115 returned safely. Twenty were lost to enemy action. Eighty were lost when they ran out of fuel and had to ditch or crash-land at night. About three-quarters of the downed crews were eventually rescued.
The Japanese carrier air arm never recovered. After the battle, Japan had enough trained pilots to man the air group of only one light carrier. At the Battle of Leyte Gulf four months later, Japan used its remaining carriers as sacrificial decoys with just 108 aircraft across six ships. The surviving carriers spent the rest of the war mostly in port, and Japan shifted to kamikaze tactics in a last attempt to force negotiated peace terms.