That is two fundamentally different situations. Removing leaders by force rarely leads to stability, and generally only after quite a bit of intermediate suffering.
This is an internal election, it is a normal part of their already democratic system, and changing leaders through elections is fundamentally different than leaders being deposed by force. In fact, in a democratic system changing leaders is a very crucial feature of staying democratic: a single person keeping power for too much time risks concentrating too much power, officially or otherwise, in that person. This in turn means a greater risk of the system just becoming less and less democratic: the person on top gets used to being powerful, the people get more used to always having the same person on top, and the leader also has more power to make sure the situation stays that way.
Even with the best of intention, it also damages one of the core advantages of democracy: orderly transfers of power. When leadership changes often and peacefully, it builds procedures and expectations. If you have the same guy, with the same party, holding ever more concentrated power for 50 years, the aftermath of this person's death or retirement may see a great deal of trouble, as the mechanisms and the habit of leader change has atrophied .
Mind you, how bad this gets depends on how strong the democratic tradition of a country is and how solid the power of the leader really is: nobody was worried about germany becoming a dictatorship under Merkel, because it had strong democratic institutions and because she was in coalition governments with constant checks. And yet, her long tenure still caused some degree of discomfort at the end, and I would argue rightly so. Stepping down and letting new people take the lead reinforces the idea that power doesn't belong to the individual leader, but to the people and it is merely expressed through parties and individuals within them.
Basically: changing leaders on its own is not necessarily a net positive in quality of life, but if you are in a democratic system it is a very important part of keeping said system healthy.