Curiously, the same thing occurred in Japan around the same time period when Buddhism was actively promoted by both the royal family and struggling central state in order to consolidate and unify the country. There were indeed devotees, but Buddhism served an important political function in both early Japan and Tibet.
- Thus, while we may acknowledge genuine piety among the community of believers and the attraction of the coherent world view offered by the Buddhist message, we must conclude that Buddhism provided a unifying socio-cultural model that was promoted by Yarlung dynasty kings for political purposes.
Now there are a few points worth considering in respect to what both countries were dealing with:
- - A lack of a cohesive centralized state in a disorderly multi-tribal society.
- A landed aristocracy with their own interests often at odds with the royal family.
- Unorganized native polytheist traditions often connected with political interests at odds with the struggling central state.
- A fear of China, which in the Sui-Tang period (589-907) was visibly expansionist, well organized and extremely wealthy.
If we consider that alongside Buddhism there is always monasticism, then it makes sense that a monarch could gain the favour of a devout Buddhist populace by becoming the sole or primary sponsor of the sangha. I suspect the early leaders of Japan and Tibet had this in mind.
There is also the matter of morality and ethics proposed by the religion which presumably in a fledgling country with much tribal violence would have been appealing by leaders to promote so to placate the populace.
One other perhaps unfortunate point to admit is that Buddhism as a religion of non-violence lends itself to being easily controlled from above. Lacking the means to forcefully resist, and dependent on certain parties for its existence institutional Buddhism is readily contained and directed by the powers that be.
If anyone else has some ideas to share, please do so.