How did the process of electing a president change after the election 1800? what caused this change?

During the election of 1800, the president and vice-president were elected separately rather than on one ticket. Jefferson received 73 votes as opposed to Adams' 65 but the Republican vice-presidential candidate Aaron Burr also received73 votes. This caused a tie and the election was thrown in the House of Representatives. The 12th Amendment remedied this situation by designating distinct votes by electors for president and vice-president.