Once the Viscount or his son died, investigators would begin looking for anyone connected to the attack. Keane already had a connection to Elara, even if it wasn't one he wanted.
She helped him when he first arrived in Valewind. Her name was connected to his residency papers, he stayed under her roof, and the examination with Delane had been arranged through her.
Depending on how much the investigators uncovered, there were enough connections to make Keane uncomfortable. If he also happened to be one of the main attractions at the tournament when the Viscount died, it would give them another reason to look at him.
Keane didn't fear being questioned. He simply had no interest in volunteering himself for it, especially when the people who committed the assassination might try to leave evidence pointing elsewhere.
The tournament would also restrict his movement.
