Partly because they had witnessed the amount of work the previously troubled Melbourne star put in over summer and saw his dazzling Giants debut coming.
Oliver starred alongside five-goal hero Jake Stringer in the opening-round victory over Hawthorn as the high-profile pair showed they still have what it takes to be match-winners.
"There were a few guys who performed well on the weekend and you could almost really feel it and see it coming from three or four weeks ago," GWS forward Jake Riccardi told reporters on Monday.
"Stringer was obviously one - he kicked five - and you could see his work he put in late to be ready ... and then Clarrie's another.
"His last month was unbelievable and he really stepped up.
"With Tom (Green) going down, he really took it upon himself to be like, 'Righto, I've got to really fill that hole'."
Oliver stepped into the midfield breach with 26 disposals, 10 clearances and a goal in his first game for GWS after 205 with Melbourne.
He admitted post-match he had arrived in Sydney "pretty unfit to be honest, a little bit fat".
But the 28-year-old's efforts have inspired his teammates, including young forward Phoenix Gothard, who kicked the sealer on debut.
"We train pretty hard and we value that pretty highly, so I think he was a bit shocked initially," Gothard said of Oliver.
"But he's gelled in amazingly and put in a mountain of work, and you can see it in his form now.
"Hopefully he's great for us going forward because he's going to be pretty important."
Oliver's efforts helped GWS bury the demons of last year's elimination final defeat to Hawthorn and this week takes on a similar theme.
The Giants travel to take on the Western Bulldogs at Marvel Stadium, where they were thrashed by the same opponents by 88 points late last season.
It followed a 32-point defeat in round seven to the Bulldogs, who have won nine of the past 10 meetings between the sides.
"Those games are going to come but the fact that they're at the start of the season ... is probably good for us just to knock them over and get it done," Riccardi said.
"We've had results in the past where teams have knocked us over by a fair bit and we've responded.
"This week will be no different to last, I guess, in terms of rectifying what we got wrong those two times we played the Doggies last year."
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