I cannot respond without looking into what grounds are there to believe svet in proto-slavic is not related to sve.

No one speaks proto slavic, so it is all conjectures based on languages that were spoken more recently.

I believe linguist academics are citizens of their countries, and their interpretations of things in the past are influenced by languages they speak.

There's an academic field called "historical linguistics" [0]. What laypeople believe about language is called "folk etymology" [1].

[0] https://en.m.wikipedia.org/wiki/Historical_linguistics

[1] https://en.m.wikipedia.org/wiki/Folk_etymology

>No one speaks proto slavic, so it is all conjectures based on languages that were spoken more recently

Not really. Written Slavic exists since 9 century and it was spelt vs- already back then. Serbo-Croatian is an outlier here because all other Slavic languages have vs-.

Baltic languages are related to Slavic and Old Prussian had "wissa" for "all" (not "siva")

Proto-Slavic vьśi => Serbian svi, Russian vse.

Proto-Slavic světъ => Serbian svet/svit, Russian svet.

It's two unrelated words which just happen to start with the same two consonants in Serbo-Croatian out of all Slavic languages, after the phonetical change vs- => sv-

Not pretty sure, absolutely.

Also:

  svak => svako
  svit => svet