From the holocaust encyclopedia, it’s about nazis but this is close enough:

Jehovah’s Witnesses were subjected to intense persecution under the Nazi regime. Nazi leaders targeted Jehovah’s Witnesses because they were unwilling to accept the authority of the state, because of their international connections, and because they were strongly opposed to both war on behalf of a temporal authority and organized government in matters of conscience.

My understanding is that they’ve had an issue with them for some years. My guess is that it may be that the Russian Orthodox Church, which has a lot of links to the state, doesn’t like competition, and that the Jehovah’s Witnesses are kinda famous for aggressively recruiting (like, going door-to-door to try and win new converts).

kagis

https://foreignpolicy.com/2021/03/26/why-is-putin-afraid-of-jehovahs-witnesses/

On Wednesday, authorities in Russian-occupied Crimea announced that they had arrested a 30-year-old man suspected of promoting an organization that had been banned and deemed extremist in Russia. The day before that, prosecutors in the Russian city of Smolensk asked a court to sentence three adherents of the same group to up to nine years behind bars. On Monday, in the Crimean port of Sevastopol, prosecutors sought seven years for a man charged with “organizing the activities of an extremist group.”

So who are these scary extremists? Jehovah’s Witnesses, a Christian denomination with an estimated 175,000 followers in Russia. In 2017, Russia’s Supreme Court declared the group an extremist organization, lumping its non-violent adherents into the same category as neo-Nazis and members of al Qaeda.

As is often the case with authoritarian states, it’s hard to tell exactly what has prompted the crackdown—and there’s likely more than one reason. Jehovah’s Witnesses themselves are bewildered.

“If it wasn’t so serious, it would be a joke. It’s absurd. Jehovah’s Witnesses have been anything but extremist, and we’re certainly not dangerous or violent,” said Jarrod Lopes, a spokesperson for the group’s headquarters in the United States. Jehovah’s Witnesses remain politically neutral for religious reasons and do not vote, run for office, or protest. That might have spared them the arrests and harassment levied against protesters and opposition politicians in Russia, but their apolitical stance might have singled them out in other ways. “That looks very suspicious to our authorities,” said Alexander Verkhovsky, director of the Moscow-based SOVA Center for Information and Analysis, which tracks discrimination and misuse of Russia’s extremism laws.

After Vladimir Putin returned to the presidency in 2012 amid mass street protests against allegedly rigged elections, the Kremlin made a conscious effort to foment nationalism—and support for Putin. This new wave of patriotism was built around support for the armed forces and the Russian Orthodox Church, which is closely interwoven with the Russian state. All of this made Jehovah’s Witnesses—who refuse military conscription based on their faith—all the more conspicuous.

“I think it makes states that want a lot of control uncomfortable, because they can’t really control this community,” said Emily Baran, a history professor at Middle Tennessee State University.

Suspicion of Jehovah’s Witnesses in Russia dates back to the Soviet Union, when the group was outlawed and repeatedly maligned in the press, which portrayed them as fanatics and accused them of being criminals, con men, and Nazi collaborators. It created a stigma that was never undone. April 1 marks the 70th anniversary of the deportation of thousands of Soviet Jehovah’s Witnesses to Siberia during Stalin’s rule.

“I think that some conspiracy theory appeared somewhere inside the governmental structures regarding Jehovah’s Witnesses,” Verkhovsky said. “And we cannot even discuss it in public because these theories are not presented to the public.”