A really good and thoughtful question, goddaughter. Short answer: money talks! Longer answer: JFK's father was a rum-runner during US Prohibition, stock market manipulator and Hollywood financier who used his money to buy respectability--in his case, appointment as Ambassador to the Court of St. James. He also bought JFK's nomination as Democratic Presidential candidate in 1960. The Presidential election was the closest in modern US history, and Kennedy Sr. used his money and influence to throw the election into JFK's corner. JFK, notwithstanding his considerable charm, charisma and occasional leadership qualities, didn't accomplish much in his less than 3 years as President. Much of his current fame and adulation stems from the mythology that inheres in his tragic death. This isn't unusual in politics. Abraham Lincoln, considered by many (including me) to be the greatest US President, might not have been regarded as so great had he lived to deal with the problems of Reconstruction after the US Civil War. Those problems fell to his successor, Andrew Johnson, who was impeached.*
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* - "Impeached" under the US Constitution means indicted and tried for "high crimes and misdemeanors. Johnson was tried by the US Senate, but not convicted. (Sorry to be pedantic, but since you're not from the US, I thought I'd try to explain this nuance.)