DALLAS—Both trials had the same pro-Hamas videos, the same anonymous Israeli witness and the same details of how a Muslim charity in Texas routed millions of dollars to terrorists overseas.

So how did the government win such a sweeping victory Monday—guilty verdicts on all 108 counts—just a year after failing to prove its case?

Largely by simplifying a complex case of terrorism financing, and by making the most of a do-over, attorneys on both sides said.

“In our judgment, we had a strong case last year,” lead prosecutor Jim Jacks said. “We felt good about our case when it was presented. We felt like we presented good evidence. This year, we refined the case somewhat.”

The convictions of the Holy Land Foundation for Relief and Development played out like a blowout government victory Monday. So swift was the rundown of the guilty verdicts that family members in the courtroom seemed to barely have time to react.

The government’s first crack at Holy Land last year ended in a mistrial, unable to sway jurors that the defunct charity routed more than $12 million to the Palestinian militant group Hamas.

Five Holy Land leaders were convicted Monday on charges ranging from supporting a terrorist organization to money laundering and tax fraud. A sentencing date has not been set, but some could be locked away for life.

Defense attorneys plan to appeal. Lawyers for Ghassan Elashi and Shukri Abu-Baker, who were convicted on 69 counts combined, criticized what they called unprecedented use of an anonymous witness and “inflammatory” images of extremism.

Holy Land wasn’t accused of violence, but of bankrolling schools and social welfare programs the government says are controlled by Hamas. The defendants said they only fed the needy and gave much-needed aid to a volatile region.

“I believe the government tried this case using every bit of resource they has to inject fear and prejudice,” Nancy Hollander, Abu-Baker’s attorney, said Tuesday. “They spent weeks and weeks talking about totally irrelevant events—bus burnings, suicide bombings, knowing (they) were not charged with any violence.”

Defense attorneys also protested an Israel official allowed to testify anonymously that Hamas members were among the leaders of Holy Land’s benefactors. The Israeli agent, who testified under the pseudonym “Avi,” also appeared in last year’s trial.

Hollander and Linda Moreno, Elashi’s attorney, said “Avi” provides strong grounds for appeal.

Complicated and confusing was how some observers panned the government’s case last year. They called the litany of charges overwhelming and the case too hard to follow. Jurors deliberated 19 days before deadlocking on most counts.

Prosecutors responded by dropping about 60 charges and tightening their narrative. The retrial lasted seven weeks—almost nearly as long as the first trial—and some 15 boxes of evidence wheeled into court on a flatbed still impressed the enormity of the case.

Jacks said prosecutors benefited from talking to jurors last year and finding out what worked and what didn’t. He said they also brought the case back “streamlined and simplified” for a new panel.

“They kind of stripped it down to its basics,” said Matthew Orwig, a former U.S. Attorney who called last year’s mistrial a “stunning setback” for the government.

Hollander, Abu-Baker’s attorney, said prosecutors had the benefit of adjusting their case based on what the defense offered the first time around.

“Retrials are always difficult because the government knows what the defense is gong to do,” she said.

Names of the jurors in the retrial were not released. Court officials said Tuesday the panel was given a chance to talk to the media and unanimously declined.

Along with Elashi and Abu-Baker, Mufid Abdulqader and Abdulrahman Odeh were convicted of three counts of conspiracy. Mohammed El-Mezain was convicted of one count of conspiracy to support a terrorist organization, and Holy Land itself was convicted of all 32 counts.

U.S. District Judge Jorge A. Solis ordered the five men into federal custody Monday while they await sentencing.