The Cottagers' manager blamed lapses in concentration for letting the Irish league team back into the contest in the second half.
"In hindsight you could say if you score three goals away from home it's okay," he said after the hard-fought 3-1 victory at Seaview, with the goals coming from Matthew Briggs, Bobby Zamora and a Danny Murphy penalty.
Jol said he knew Crusaders would approach the game like a cup final.
"That was always the problem, so you have to motivate yourself and we said before the game they will be battling for the first 60, maybe 70 minutes and then it's probably over," he added.
"They gave us a good game, they've got a direct style with two big strikers so we had to keep concentrating over 90 minutes and that's what we didn't do with the goal."
Crusaders manager Stephen Baxter said he was extremely proud of his players
"We have given an incredible account of ourselves," he said.
"You are talking about part-time players, the gulf in footballing and financial terms is just incredible and for us to give a performance like we have and put them on the rack for a little bit, for five minutes, when we might have gone 2-1 up, maybe even 3-1 up, was fantastic."