Short answers, pulled from the story.
A combination of declining KSČ electoral support, Soviet pressure, and a strategic decision to seize power before the May 1948 elections triggered the coup. By summer 1947 the party expected to be soundly defeated at the polls, and Joseph Stalin, after Communist parties in France and Italy also failed to win power, ordered KSČ leader Klement Gottwald to take control by other means.
The government crisis ran from the 20th to the 27th of February 1948. The decisive moment came on the 25th of February, when President Edvard Beneš accepted the resignations of twelve non-Communist ministers and appointed a new Communist-dominated government in accordance with KSČ demands.
Beneš feared civil war and Soviet military intervention; the Red Army was stationed on the country's borders and Soviet deputy foreign minister Valerian Zorin had arrived in Prague to help coordinate the coup. Historian Igor Lukes also noted that Beneš had been in poor health since 1945 and by 1948 lacked the physical and emotional stamina to hold out against the KSČ.
Jan Masaryk, the only senior minister in the new government who was neither a Communist nor a fellow traveller, was found dead two weeks after the coup outside a third-floor window. An investigation closed in 2021 concluded that murder, accident, and suicide all remain possible explanations.
Congressional opposition to the Marshall Plan collapsed in the wake of the coup. Public outrage at events in Prague led Congress to promptly approve over five billion dollars for the first year of the European Recovery Program.
The coup accelerated Western security cooperation. British Foreign Minister Ernest Bevin used the crisis to press the United States for a formal military alliance; European leaders began meeting secretly with U.S. defence and diplomatic officials at the Pentagon that spring, and the Treaty of Brussels was concluded the following month. NATO was formally established just over a year after the coup.