TBH, not a huge fan of Sylas' lore
The first thing that gets me about his lore is that it seems like it shares too much with Urgot's lore. Both people who dutifully and happily worked for their mother countries, but end up imprisoned and resent their home for its societal structure. Both learn things that make them stronger in prison and break out to lead revolutions based on their newfound visions of destruction. The draw more similarities between the two, Urgot's line "They put me in chains, they gave me my weapon!" could be used for Sylas almost too perfectly. Both also have lines about toppling the walls of Demacia and discord/chaos being better than order. I know there are nuances and differences between them, but it almost feels like a Pyke vs. Old Nautilus situation again.
The other thing that irks me is that he was not killed outright. Demacian officials painted him as "one of the most dangerous mages in Demacia" and he killed three members of high society while originally being a member of low society himself. There are so many factors that suggest he should be killed outright, but he is instead imprisoned and given time to gather knowledge and power.
IDK, those a couple of things that made me not feel invested in Sylas' lore. It's just my few cents on the matter that I felt like sharing.