Mahāyāna Buddhism influenced temple designs more in certain Southeast Asian regions—such as Java (Indonesia), Sumatra, and Cambodia—primarily due to a combination of political patronage, cultural exchange along maritime trade routes, and the syncretic adaptation of local traditions with imported Mahāyāna beliefs.

Key reasons for this regional influence include:

• Maritime Trade and Cultural Exchange: Regions with extensive maritime trade, such as the Srivijaya Kingdom (Sumatra), Sailendra dynasty (Java), and the Khmer Empire (Cambodia), were major conduits between the Indian subcontinent, China, and Southeast Asia. These networks facilitated not just the movement of goods, but also Buddhist monks, pilgrims, and architects, leading to strong Mahāyāna influence in religious structures.

• Royal Patronage and Buddhist Kingdoms: Powerful rulers in these areas adopted Mahāyāna Buddhism as state ideology and sponsored grand temple projects to project authority and spiritual legitimacy. For example, the Sailendra dynasty built Borobudur as a vast Mahāyāna Buddhist mandala, and King Jayavarman VII of the Khmer Empire transformed Angkor Thom with Mahāyāna symbolism and temple designs like the Bayon, visually representing Buddhist cosmology and the king as a bodhisattva.

• Syncretism with Local Traditions: Mahāyāna Buddhism proved highly adaptable and was often blended with indigenous beliefs, local deities, and traditional rituals. This syncretism encouraged unique forms of temple art and architecture incorporating both imported Mahāyāna iconography (bodhisattvas, mantras, cosmological symbols) and local cultural expressions, unlike the more scripturally conservative Theravāda traditions of mainland Southeast Asia.

• Artistic and Scriptural Diversity: Mahāyāna Buddhism embraces a broader pantheon and diverse body of scriptures, which inspired more elaborate and symbolically rich architecture—evident in the reliefs, mandalas, and bodhisattva statues at sites like Borobudur, and in the integration of Hindu and Buddhist themes at Angkor.

By contrast, regions such as Myanmar, Thailand, and Laos became strongholds of Theravāda Buddhism from the 13th century, favoring simpler monastic complexes and stupas emphasizing scriptural orthodoxy rather than the visual and cosmological exuberance of Mahāyāna-influenced temples.

In summary, Mahāyāna Buddhism's architectural influence was strongest in parts of Southeast Asia that were major participants in maritime trade, had rulers who actively promoted Mahāyāna ideals, and fostered a high degree of religious syncretism, resulting in monumental and syncretic temple complexes that endure today.