The revelations add an uncomfortable dimension to O'Neil's departure, which was already the second time in six months that Strasbourg had lost their head coach unexpectedly — Liam Rosenior left for Chelsea in January, and O'Neil was appointed as his replacement.
The 43-year-old had been involved in multiple recruitment discussions and gave no indication he was considering leaving. According to L'Équipe, his contacts with Ipswich existed throughout that period, but he disclosed nothing to Strasbourg's directors until the move was effectively done.
O'Neil was candid about his reasoning at his Portman Road unveiling.
"Coaching in the Premier League — I couldn't turn it down. The Premier League is the summit of a career and it corresponds to my personal ambition," he said.
He had reportedly also felt that Strasbourg's failure to qualify for European football next season represented insufficient sporting guarantees for his ambitions.
Ipswich paid around €5m in compensation to release O'Neil from a contract that ran until 2028. Strasbourg are now searching for their third manager in less than a year and are understood to be considering another English coach as successor.
The €5m fee also raises questions about the value of managerial contracts within the BlueCo group, where the interconnected ownership of Chelsea, Strasbourg and other clubs creates obvious pathways that make it difficult for smaller clubs in the group to retain ambitious coaches when Premier League opportunities arise.