When rome first started people were not focused on conquering, people were friendly and didn't think about taking over. Before The Pax Romana Augustus Caeser was ruler and he was greedy and selfish, He was ignorant and made one of the biggest mistakes.
Augustus took over everywhere and thought he would be the best ruler, but the Rome council thought otherwise. The council thought and came up with a plan to end Augustus Caeser's reign.
They executed Augustus and so came another ruler, every ruler was ignorant and caused Rome to start it's end. This happened because the government started to fall under the hand of its rulers, and then other countries took over and eventually Rome died.