Are Bulgars the only Turkic people that got assimilated to other cultures?

If we look at history, one fascinating fact about the old Turks/Turkic people is that they possessed a strong assimilation power. Wherever they travelled and ruled, they usually were able to assimilate the native people of the land they conquered, especially linguistically, albeit absorbing many elements of local culture in the process. I guess this is one of the reasons why the Turkic people expanded from several tribes in Altay and Otuken to build empires and kingdoms, changing the history of much of Asia and Europe and still keeping their Turkic identity.

However, to my knowledge, the Bulgars are the only exception where a Turkic ruling group assimilated into Slavic culture and adopted a Slavic language. What do you think is the reason? Are there any other Turkic tribes that got assimilated?