Even the Romulan-heavy Star Trek: Picard Season 1 avoided addressing or explaining the supernova in any detail.
Explaining? Stars go supernova occasionally, there’s your explanation. There doesn’t need to be further cause or intervention behind it.
IMO this is a solution (or really several) looking for a problem that just doesn’t exist. As it stands and despite fan speculation, Romulus was destroyed by a natural disaster, which is actually something that happens on Earth and in the wider universe.