"It's obviously great for Tonga, and great for the game," Hopoate said.
"It's building the game internationally and I think it will make the World Cup a bit more competitive."
Fifita's decision to withdraw from Australia's squad for Tonga will cost him a $30,000 tournament payment as well as a possible $20,000 payment if the Kangaroos win the World Cup.
Instead he'll join a Tonga squad receiving a $30 per diem during the tournament, which starts on October 27.
"It's a big stand what they're doing and obviously courageous of them to do so," Hopoate said.
"There's obviously a lot more benefits playing for the Tier One nations and they're clearly not doing it for money, rather for passion, for pride and it's great for the game."
Hopoate said he was unaware of a reported pact between the New Zealand players to choose Tonga over the Kiwis in protest against New Zealand coach David Kidwell.
Taumalolo and the other Kiwi-eligible players are believed to be upset with Kidwell's decision to overlook Jesse Bromwich and Kevin Proctor after the pair breached team protocol following this year's Anzac Test against Australia in Canberra.
The influx of talent to Tonga's lineup has resulted in them shortening to fourth-favourite in betting markets for the tournament behind Australia, England and New Zealand.
Priced at $81 with the TAB before news of Taumalolo's defection broke, Tonga have come in to $17 with more bets placed on the Pacific Islanders in the past two hours than in the past two months.
"It is a boost for us getting these boys ... there's no secret to that but just because their name's on a piece of paper doesn't mean we're going to play magically on the field," Hopoate said.
"It's going to take hard work, it's going to take a few tough training sessions ... training hard and being consistent with what we do off the field will help us perform on the field."
Tonga's World Cup Squad
Andrew Fifita, Mahe Fonua, David Fusitu'a, Siliva Havilli, Ata Hingano, Will Hopoate, Konrad Hurrell, Michael Jennings, Solomone Kata, Sione Katoa, Samisoni Langi, Tuimoala Lolohea, Sika Manu, Manu Ma'u, Sam Moa, Ben Murdoch Masila, Joe Ofahengaue, Tevita Pangai jnr, Ukuma Ta'ai, Sio Siua Taukieaho, Jason Taumalolo, Peni Terepo, Daniel Tupou, Manu Vatuvei