“At this stage, all I know is that the most likely motivation behind the assassination could have been financial disputes between Mr. Karimian and his wide networks of business partners from Dubai to Malaysia,” said Ali Vaez, the senior Iran analyst for the Crisis Group, a research institute focusing on international affairs.

Others sensed the hand of the Iranian state. The National Council of Resistance of Iran, an exiled opposition group, claimed that Mr. Karimian was assassinated by Iran’s Revolutionary Guard on the orders of Ayatollah Ali Khamenei, the country’s head of state. Iran has been accused of assassinating Iranian exiles in the past, most recently Abbas Yazdi, an Anglo-Iranian businessman who was kidnapped in Dubai in 2013 and is now thought to be dead.

In January, an Iranian court announced in a judicial newspaper that Mr. Karimian had been sentenced to six years in prison for spreading propaganda against the country’s Islamic government, and acting against national security. The Iranian government sees westernized entertainment, such as the types of series broadcast by Mr. Karimian, as a threat to the conservative society it has built in Iran since seizing power in a revolution in 1979.

While satellite dishes are banned in Iran, they are widely used, and millions of Iranians watch Gem’s programming. “The regime is very sensitive about culturally subversive media and entertainment broadcast from overseas,” said Karim Sadjadpour, an Iran expert at the Carnegie Endowment for International Peace. “Khamenei believes this is precisely the U.S. strategy — to overthrow the Islamic Republic via a soft revolution,” he said.

Mr. Karimian had suggested that he hoped his work would change Iranian society. “We will do our best to create an Iran one day that we can take pride in,” Mr. Karimian said in comments that were broadcast posthumously on his own network on Sunday. Analysts said it was possible that Mr. Karimian might have been targeted by the state. “One cannot rule out the possibility that he posed a serious threat to a powerful stakeholder in Iran,” Mr. Vaez said. But he added that Mr. Karimian “doesn’t fit” the profile of someone important enough for the Iranian government to assassinate on foreign soil.