Why do you need mass for the sun to explode

It has to do with the end of star life, when our Sun reaches it, it will not "explode" in a Nova because it's core will not be large enough when it collapses to create it, there won't be enough gravity to create a threshold amount of matter compression making it nova.. Larger stars than our Sun will Nova or Super Nova at the very end of their lives because they will have a much larger cores to collapse due to more matter and heavier elements being created at the end of the stars life, this will make for a much heavier/higher gravity force which will push the core to the point of "exploding" big time when gravity finally beats nuclear fusion furnace in the stars core.

the sun is a fusion reactor... without a critical mass, a chain reaction isnt possible.

look up critical mass.

Because our sun doesn't have enough mass to use the CNO cycle

idk