I am NOT a historian/expert. This explanation might be wrong.

Most women leaders of eastern countries were either related to or were closely mentored by male leaders. These male leaders were very charismatic and larger-than-life, and thus, after their death, people wanted the person closest to them lead the way. The person closest to them were either their wife, daughter or mentee.

This works out well because the charismatic male leader generally creates a revolution and "founds" a new system, while the female leader after them, does conflict-resolution between subordinates, takes care of compromises and brings in stability of the new order.

Conservative countries also tend to have a feudal multi-tier power distribution in politics, and the central government is a loose alliance of multiple sub-groups.

In this case, the subordinate leaders show hyper-masculine authority within their sub-groups and prefer to have a nurturing mother-figure as the top-most arbitrer amongst themselves as opposed to one of them seizing power. Having a woman at the top prevents an ego-clash between the subordinate men or an attempt at in-fighting.

This does not mean women play passive roles. It means men prefer ideological purity while women prefer practical stability. Many women leaders initially entered politics playing the role of a passive proxy, but over time, accumulated enough power and respect to be seen as a hard-core masculine leader, no different from male leaders. But the entry-point of women have always been due to the death of a male leader.