Why were there 5 treaties ending ww1?

These were to deal with the countries who lost the war (i.e. against the Allied Nations)

These treaties were:

1. Treaty of Versailles (dealt with Germany)

2. Treaty of St. Germain (dealt with Austria)

3. Treaty of Trianon (dealt with Hungary)

4. Treaty of Neuilly (dealt with Bulgaria)

5. Treaty of Sevres (dealt with Turkey)

The main reason for these treaties was to demilitarise the armies which prevented them from becoming threats to the Allied nations any time soon.