The explosive wing/centre still had a year left on his contract at KCOM Stadium but Hull reached a financial agreement with him to leave earlier this month.
Fonua, who won the Challenge Cup with his first spell at FC in 2016 and 2017, swiftly joined up with Castleford Tigers for 2022.
The deal freed up space on Hull's salary cap and overseas quota to complete the signing of New Zealand Warriors prop Kane Evans this week.
Speaking publicly today for the first time about 28 year-old Fonua's exit, Hodgson said: "I think it was good for Mahe and good for us a club to go in that direction.
"What Mahe is is a great bloke. He's had a great history for us as a club and we respect what he's done for us at the club and in particular the Challenge Cup performances.
"He's quite an iconic figure for the club and we wish him all the best and myself personally, I had a conversation with him once he signed for Cas.
"I hope he's successful. Not against us next season obviously!
"But he's gone there and hopefully he will be successful at that club."
After joining from Melbourne Storm, Fonua scored 31 tries in 58 games for Hull and was named in the Super League Dream Team for 2016 and 2017.
He returned to the NRL with Wests Tigers for two seasons but struggled to recapture that sort of form in his second stint in East Yorkshire - something he now hopes to rekindle under his former Hull boss Lee Radford at Wheldon Road.