First of all, it is important to highlight that a strong central government does not equal an autocratic one. However, if you are comparing governments with a single leader that has a lot of power and governments with a more balanced distribution of power, then autocratic governments tend to be less stable than governments who distribute power among several leaders.
The main reason for this is that a single, strong leader can be more conducive to abuse and corruption. If every decision depends on the judgement of a single person, that person might feel tempted to use power for his own benefit. This reduces accountability to the people, and leads to personal interests being more important than the interests of the nation.
On the other hand, when power is well-distributed, institutions have a system of checks and balances. This means that it is much harder to abuse power. It is also more difficult to put your interests ahead of the nation's interests. Finally, this strategy leads to slower change because it requires dialogue and cooperation, and slow changes usually contribute to stability.
