Tell me why they created the 12 amendment

The experiences of the 1796 and 1800 presidential elections – showing that the original system caused the election of a President and Vice-President who were political opponents of each other, constantly acting at cross-purposes – spurred legislators to amend the presidential election process, requiring each member of the Electoral College to cast one electoral vote for president and one electoral vote for vice president. Under the new rules, a contingent election is still held by the House of Representatives if no candidate wins a presidential electoral vote from a majority of the electors, but there is no longer any possibility of multiple candidates winning presidential electoral votes from a majority of electors. The Twelfth Amendment also lowered the number of candidates eligible to be selected by the House in a presidential contingent election from five to three, established that the Senate would hold a contingent election for vice president if no candidate won a majority of the vice presidential electoral vote, and provided that no individual constitutionally ineligible to the office of president would be eligible to serve as vice president.