One could argue that figher jets were not used at that time to keep the pretence of legitimacy of the entire episode. And that pretence is important, because when you publicly declare that the force is now the standard, the most unscrupulous bully wins over bullies with moral limits or political liabilities. Belarus, on the other hand, in its current political environment has no image to lose.

One could also argue fighter jets weren't used at the time because none of the states involved planned for Morales' pilot to identify an issue with his fuel gauge and request permission to land, which has the neat property of being consistent with the hard evidence as well as not involving the whole of Europe's ATC coming up with the clumsiest plot ever to detain someone who wasn't actually there, particularly significant to Europeans or any easier to arrest in Vienna than the originally scheduled stop in the Canary Islands

Someone should let the Bolivians know because they missed that bit from their accounts!