Hotel Lux was a hotel in Moscow where foreign Communist leaders who fled to Russia were held captive from the 1920s and into the 1950s. It existed from the time of the Communist revolution and was only disbanded with Stalin's death. The paranoid Soviets ruled with an iron fist also against their own, purging anyone who they deemed as unreliable.
What happened in Hotel Lux is still shrouded in mystery for the most part. All we know is that it was notorious and even "good" Communists had no chance of surviving and ended up in the Gulag. Others who survived Hotel Lux, like Western German SPD politician Herbert Wehner later kept insisting that their experiences there lead to them "breaking with Moscow".
Hotel Lux must have been a horrible experience, the question is just: Why exactly? It's apparent the inmates weren't treated badly, because this is what the Gulags were there for. It was also in Moscow right at the center of Communist power. Last but not least, we're talking about the future elites of Communist rule over Europe, and you better treat your apparatchiks well, or they may turn against you eventually.
It's also doubtful they were constantly surveilled for heretic thoughts, because there was no reason for such thoughts: The early Communist revolution was a desired project by everyone and everyone was well aware that such things go down with brutality. Both, their philosophical underpinnings as well as the memory of the French Revolution make it clear that when push comes to shove, you use raw violence and a lot of it. Last but not least most Communists experienced WW1 in one way or another and were accordingly desensitized towards violence, especially against those who they saw as responsible of the carnage.
Therefore there must have been something else by which some cadres were deemed reliable and others haven't. This something else also must have been something so heinous that nobody would ever talk about it in public, even if they end up dissenting like Wehner, and which at the same time makes them loyal in a way that ascends over national, religious or other affiliations.
Communists don't see morality as guiding principle, but only power. They also see Western bourgeois society as the root of evil and therefore everything it stands for: Monogamy, church, chastity and the protection of the weak, while projecting their own power. As we know of Gramsci and Lukacs, the best poison against this is sex and a lot of it from a young age onward and with no limitations to whatever sexual desire someone has. Not only does this annihilate the ideals of bourgeois society, but is also an expression of total power: Nothing is more potent than immediate total sexual power over someone else.
This is why I believe the true selection filter applied in Hotel Lux was sexual deviancy. Those Communists cadres who engaged in it - homosexuality, bestiality, BDSM, rape, pedophilia - survived and were allowed to rise to power, whereas those who didn't like it, were deemed unreliable and had to go. The shared intense sexual gratification made sure the survivors had a common positive experience and made sure they had a shared secret, it also separated them forever from any kind of bourgeois lifestyle, filming everything made sure there was enough kompromat for dissenters and lastly, why would anyone care for anyone or another cause, when their deepest sexual desires would be fulfilled to the fullest extend whenever they wanted?
There can be no other conclusion than that Hotel Lux was funnel for sexual deviancy. While there is no direct evidence, there are various indications of the true (homo-)sexual nature of Communist leaders of the Communist world:
I'm not sure about Wehner's motives there, it was legal as both were adult and officially he did it to ensure her a good pension. But it's not too far away to speculate he may have been accustomed to the incest lifestyle himself too much. It's a known phenomenon that extremely close relationships emerge among family members when the barrier of incest has been broken.
What I still do see is that while Wehner and probably others did live a secret lifestyle of illegal sexual practices (especially during their vacations in Sweden), they may have retained their moral sense and knew about its toxicity for society at large. This lead them to break with the Comintern, whereas others like Chancellor Brandt lived it more or less openly, or even excelled in the utilizing of sexual kompromat for intelligence like Markus Wolf, who was more or less the Jeffrey Epstein of the Cold War.
What do you think, is this plausible and are there other indicators for Hotel Lux being a sex blackmail operation?