The idea for the prequel, came from a conversation that creator Steven S. DeKnight had with actor John Hannah. Hannah's character had been killed off in the first season, but Hannah enjoyed working on the show so much that he told DeKnight he'd be more than willing to continue working with it somehow. As it was, production of the second season was on hold due to the declining health of star actor Andy Whitfield. So DeKnight's idea to shoot a prequel to season one was the ideal way to continue working with John Hannah and give audience members something to "feast on" until season two could go into production.
The prequel is not just about how Crixus became the Champion of Capua and how Quintus Batiatus became the owner of the gladiator school. It is also about Lucretia's dark transformation into the evil woman she became.
The opening scene of the first episode which was a recap of the finale of Spartacus: Blood and Sand (2010) (TV Series) was speculated to had influenced the opening scene of the 30th anniversary special of the long-running British soap opera EastEnders (1985) (TV Series) which was a prequel and detailed the final hours of the life of one of it's regular characters Lucy Beale (Hetti Bywater).
It is unclear why Titus dislikes Lucretia and why he ill treats her. It's likely Titus dislikes his daughter-in-law because she is corrupting and influencing Quintus which Quintus is consumed by his ambitions and pursuit of money, power and political status.
The trivia items below may give away important plot points.
SPOLIER: The prequel reveals how Quintus became successor of the House of Batiatus. How Crixus became a gladiator and champion. How Crixus became Lucretia's lover. How Oenomaus became Doctore and shows Lucretia's dark transformation. (Symbolized by the red hair)