When Robinson was recalled, England director of cricket Rob Key said he looked “back up to his full fitness”.
“When you look at his record he is one of the bowlers right up there statistically, among all the bowlers, of all time,” Key added.
Robinson has started the season well with Sussex, captaining them to three wins out of six games in the County Championship and taking 18 wickets at 26.27.
However, Broad, who took 604 Test wickets, said he is intrigued why Robinson has been recalled now having seemingly fallen out of favour with head coach Brendon McCullum and captain Ben Stokes.
“I’d love to know what the turnaround has been – has he suddenly improved his fitness or improved his attitude because he was never left out because of performance,” said Broad.
“Not that these guys have ever said this to me, I thought McCullum and Stokes had lost faith and lost trust and that was the end of that.
“I suppose it’s probably a case of who else will take the new ball? The new-ball bowling in the Ashes was awful and they need a new-ball bowler.
“There’s no doubt Ollie is the best new-ball bowler available to England in the country at the moment. He has amazing ability to get the new ball to talk and he gets bounce.
“Rob Key said he’s a world-class bowler at 82-83mph and the test for Robbo is if that 82-83mph stays over three Tests and for every spell without him going off or missing sessions.
“Not many bowlers get another chance when you have been written off for character and attitude.”