Mahayana explicitly rejects the idea of a Creator, just as Theravada does in the Brahmajala Sutta of the Digha Nikaya (and in at least nine other passages). The Mahayana teachers Asanga (4th century), Dharmakirti (7th century), Chandrakirti (7th century), and Shantideva (8th century) each explicitly refuted theism. Among the Mahayana Sutras the Rice Sapling Sutra in its doctrine of causality is understood by His Holiness the Dalai Lama to imply nontheism (see his remarks in Healing Anger). The idea of a Creator is excluded by several basic Buddhist doctrines, including Not-Self, shunyata, the impermanence of all samskaras, dependent origination, and karma and rebirth.
I am not aware of any "followers of Mahayana" espousing theism prior to the 20th century. The view is heterodox.
I should dispel the suffering of others because it is suffering like my own suffering. I should help others too because of their nature as beings, which is like my own being. When happiness is liked by me and others equally, what is so special about me that I strive after happiness only for myself? When fear and suffering are disliked by me and others equally, what is so special about me that I protect myself and not the other? Shantideva, Bodhi[sattva]caryavatara 8.94-96