The defeat left Treviso still searching for a first win on Irish soil since December 2011 but they remain eighth in the RaboDirect PRO12 table as Leinster solidified third position behind Glasgow Warriors and leaders Ulster.
Leinster were dominant from the first whistle as they spent the majority of the opening exchanges inside the Treviso 22 and it wasn't long before the first try came courtesy of Ryan.
The flanker had control of the ball after a successful lineout and pushed over to score his first try of the season but Ian Madigan missed with the conversion.
And just three minutes later they were further ahead thanks to a brilliant score from Irish international Cronin. Upon received a pass from Luke Fitzgerald, the hooker ran the length of the pitch to touch down.
Madigan this time however was successful with the extras from a tough angle before James Ambrosini missed a simple penalty for the visitors, summing up their start.
Madigan was soon called into action again when Ryan crossed for his second try of the evening in what was a carbon copy of his first. The fly-half duly converted and Leinster had raced into a 19-0 lead after just 23 minutes.
They required just one more score to seal the try bonus point against their Italian opponents and that came in the 27th minute when Cronin, not to be outdone by his teammate, grabbed his second of the evening, throwing a great dummy and putting on the gas to score under the posts.
Madigan converted and it was 26-0 with not even half an hour played and that was how it stayed until half-time with Treviso lock Marco Fuser's substitution for Filippo Giusti the only other action.
But clearly boosted by his first-half efforts, Ryan came out to complete his hat-trick six minutes after the restart with a familiar conversion from Madigan to take the score on to 33-0.
However the home fans were slightly surprised by a spirited Treviso side who then got their first points of the evening with a try of their own, courtesy of wing Ludovico Nitoglia, although Ambrosini couldn't kick the extras.
Both sides made a whole host of substitutions around the hour mark and it was one of the home side's fresh blood that made an instant impact, Leo Auva'a going over in the 69th minute.
Wing Fergus McFadden took over kicking duties after Madigan's departure and converted the try to seal a 40-5 victory for Leinster keeping them very much in the play-off race.
|Leinster Rugby Score Card|
|Benetton Treviso Score Card|