The Cottagers' manager blamed lapses in concentration for letting the Irish league team back into the contest in the second half of Thursday night's Europa League second qualifying round, first-leg tie.
"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."
The Fulham boss said the encounter in Belfast had been good for his side, expressing hope that the players would wake up unscathed from 90 minutes on the artificial surface at Seaview.
"It was okay, the hotel was fine, the only problem was maybe the pitch, but hopefully tomorrow everybody will say it was good experience," he said.
Jol said he was also pleased with the form Bobby Zamora was showing ahead of the start of the new Premier League season.
"He's a goalscorer, so if he's scoring goals I am happy," he said.
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 tonight 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."
Baxter said Fulham's class had told in the end.
"They carved us open with balls up to Zamora and the movement of (Andrew) Johnson, class players who you could see had these extra gears and were fabulous."
He added: "But we have given them a game and that's important for Irish league football - we were flying the flag a little bit for what we do over here at part-time level and I think we did it particularly well.
"We've created two or three really good chances at this level of the game and when we went 1-1, my word, I thought the house was going to cave in and it was fantastic. So I am more than pleased, I am ecstatic at how well we've done."
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