Bhudhisam is always told as a rebel religion. It is a rebel in the sense that it is the first religion which declared that there is No GOD.
Bhudha's primary teachings are:
1. World is Maya and Illussion. 2. Once you remove this maya, then you will realise that there is nothing. Soonyam, ( where as Advaita says, once the maya is removed you will realsie infinity ie Brahman) 3. When there is No God, then No Vedas/Havans either. ( Please note he is against Havans not because they had animal sacrifice but because he believed there is no god. He himself died because of indigested pork)
After his death, immediately the Sangh divided into Two.
The mahayana had:
1. made Bhudha himself God. 2. Then lot of sub Gods developed. 3. To convince the masses on why there is so much difference among human birth, the Karma and Rebirth principles of Hinduism were included. 4. Elaborate Rituals for the God ( Bhudha) were introduced. 5. Big Stone temples and idols to capture the imagination of Public were introduced. 6. Havans were taboo because it is the only thing that can be differentiate Bhudhism with Hinduism.
Now please note that this repacked Bhudhism was propagated and not the original one as declared by Bhudha.
This repackage became like Pepsi and Coke ( Hinduism) agressively counterd this repackage. It is mandan Mishra/Kumarilla Bhatta who vanquished Bhudhism and not Sankara.
Where as for the other countries the new religion ( which is almost Hinduism w.o vedas and new vedas for them created. The new religion had every thing of Hinduism ) and hence appealed to all and spread.