There's a bit of nomenclature confusion involved. In early Rome, one of the two most elite social classes was the Equestrians. Their distinguishing feature was that they were super-wealthy (though not as much so as the Senatorial super-elite) and for a limited period in Roman history could correspondingly be expected to furnish themselves with battle-ready horses and serve in the early Roman cavalry. To early modern translators, this sounded like their understanding of knights, so a lot of translations employed the word 'knights' for Equestrians, without much critical thought. But in reality, a 'knight' as we understand it is a specific historical construct of a specific sort of feudal society, and aside from the fact that both Roman Equestrians and feudal knights both fought from horseback (at a very specific time in early Roman history) and tended to be moderately wealthier than the average person, they don't really resemble each other at all. For one example: knighthood is a militarized political rank in a feudal society which can be earned by people of almost any social or financial class, whereas Equestrianism was a largely heritable social and financial class status in Roman society that was assigned a military role based on wealth levels.

In this specific literary context, the soldiers were employing their knowledge of the historical past and ritualized present (in which Equestrian status was associated with a mounted military cavalry role, although active Roman armies of the period tended to rely on non-Romans for most of their cavalry purposes in Caesar's day) to make a joke that he was elevating their social class by giving them horses to ride. Later translators took that and substituted the very specific feudal ritual of 'knighting' in a somewhat confusing fashion.