Cassidy came out on top in what proved to be a three-way battle for honours in the closing stages of a race characterised by extreme energy saving and pack racing for most of the distance, before the pace picked up for the closing stages.
Both Dennis and da Costa enjoyed stints leading the race at various points of the race, but in the end both Porsche powertrain users were beaten by the Jaguar-powered Envision machine of Cassidy, who was able to break free in the closing stages and beat Dennis by 0.294 seconds.
Looking back on his third straight second-place finish, new championship leader Dennis admitted that leading the opening laps from pole put his race on the back foot strategically early on.
The Andretti driver also feels he lost out being the only one of the top three to take his second attack mode activation after the second safety car period, caused by a crash for Nico Muller.
"The pole position helped for the [three bonus] points, but it was a negative to start on pole," said Dennis. "We led the first four laps, and I was already one percent [of energy] down on Antonio.
"We pulled it back in the middle of the race, we did some risky towing, we were back in the pack and it was just mental back there. But at that stage Nick and Antonio were out front and kept it clean.
"We got a bit unlucky with the second safety car with the attack [mode], we got back to P7 with five or six laps to go. We had a lot of work to do and I got Antonio at the end.
"We just need to refine everything, when to lead, when not to lead; that’s something Envision has got a good grasp on, better than us. We had the car to win, but we just need to find some things."
Da Costa meanwhile was the first driver to seriously up the pace when he grabbed the lead on lap 22 of 32 from Cassidy, but he couldn't sustain the pace and was passed again by the Kiwi several laps later.
The Porsche driver struggled in the closing stages, slipping behind Dennis, and was left to rue pushing too early.
"I am happy with the podium but I’m a bit disappointed because I executed the race how we planned, and ultimately it wasn’t the right strategy," reflected da Costa. "It’s something we have to go back and review.
"These two guys [Cassidy and Dennis] were a bit cleverer, they planned it better than us and I struggled a bit with energy at the end.
"I thought it was the right moment to go based on our simulator work. I think we have to refine those tools a little bit, because it was slightly too early.
"That’s why I am disappointed, because in my mind it was the right time to go, but clearly it wasn’t."
For his part, Cassidy credited his victory to a "fantastic car" after securing a third triumph of the season following wins in Berlin and Monaco.
"I think it played out more or less as we expected," reflected the Kiwi. "It was probably one of the most difficult races we’ve had in terms of car balance. Antonio looked like he was struggling a little bit also, but Jake was next-level.
"To do something special or different to overcome the balance deficit wasn’t easy."
