How literally was that translated though? Ngram viewer shows [0] plenty of usage of 'of a thousand suns' well before that 1944 translation [1], though it certainly picked up after that, no doubt helped by Oppenheimer quoting it (that translation specifically, recently published at the time) w.r.t. the Manhattan project.

Confusingly [1] links to the passage in a different (1909-14) translation [2] which features the 'of a thousand suns' part but is otherwise different.

I just wonder, for example if the original was something like लक्षाणाम् सूर्याणाम् 'lakshāñām sūryāñām' (I think that's what I mean, I'm learning Hindi not Sanskrit! Just looking up लाख & सूरज roots.) but translated to 'thousand' on the basis that it just meant 'a lot', and that sounded better in English and was perhaps even already a phrase.

I don't mean to doubt you, just thought it was interesting, and translated texts are a bit of a can of worms.

[0] - https://books.google.com/ngrams/graph?content=of+a+thousand+...

[1] - https://www.bartleby.com/73/123.html

[2] - https://www.bartleby.com/45/4/11.html#44