Despite trailing by only seven points at halftime, the Lions looked short of ideas and faded after the break, allowing Leinster to take control and run in three more tries in the closing stages.
The visitors suffered an early setback when flank Ruan Venter was forced off injured just five minutes into the contest, shortly after Leinster had opened the scoring through Jamie Osborne.
Leinster eventually extended their lead in the 25th minute when prop Thomas Clarkson crashed over from close range, with Prendergast converting to make it 14-0.
The Lions responded well and finally found reward five minutes before halftime. After building pressure through their forwards, captain Francke Horn forced his way over the tryline, while Smith added the extras to cut the deficit to 14-7 at the break.
The visitors continued to show fight after halftime and created several promising opportunities, but struggled to break down Leinsterâs defence as their attack became increasingly predictable.
Despite staying in the contest for much of the second half, they struggled to turn possession and territory into points.
Instead, Osborne grabbed his second try in the 70th minute after slicing through down the flank, with Ciaran Frawley converting to stretch the lead to 21-7.
That score broke the Lions' resistance and Leinster quickly added a bonus-point try through All Blacks centre Rieko Ioane, who finished out wide after a slick move that got the better of the Lions defence.
Jimmy O'Brien then crossed late on to seal a convincing five-try victory for the Irish side, as the Lions were left to lick their wounds.