The issue isn't whether the jury would have liked the victim. The question was "did the victim attack Kyle?". The fact that the victim had a known violent past is very relevant to that question.
Courts use a victim’s (or a perpetrator’s) character in almost every trial. The prosecution used Rittenhouse’s tiktok username and about me section as a way to paint him as a killer driven by fame. The goal is to determine if the person is guilty or not.
2. The defense needed to present a motive for Rosenbaum's having attacked Rittenhouse, and they felt his prior convictions helped establish that motive.
3. The judge did not allow the defense to bring up Rosenbaum's prior convictions in court.