My personal opinion:

Buddha was a rebel who challenged the brahman and vedic supremacy .and his discourse to his disciples became what is known to us as buddhism.

he had no intention of having followers or starting a cult but it was just like all other yogis/tapaswais of his time-sharing personal experience and discoveries.

he challenged the concept of saguna(with form/character) god but still believed on gods nirguna aspect.

To attain nirvana and to get mokshya by uniting with the parabrahma is the same.Have ur say.