Almost all of this story was first posted in The Times in London. The part about the bribes hasn't been confirmed yet which makes some of this post speculation. However this very learned conjecture makes perfect sense. This is one of those 'stop what you are doing and read this now' posts.

I am going to tell you a story which explains how and why Vladimir Putin (and the Russian military) so horribly misjudged the Ukrainian war, a war, the outcome of which, will change the future of our planet Earth.
It is well known that Sergey Beseda, head of the FSB 5th-Branch (Ukraine portfolio), has been arrested, along with his deputy, Anatoly Bolyukh. (The FSB is basically the former KGB.) (Beseda is a very high-ranking spy, his rank the equivalent of a U.S. 4-star general, Bolyukh a 3-star.)

It is also known that Beseda and Bolyukh were arrested for something that at first glance seems rather strange--embezzlement from the state. Publicly unknown, but interesting indeed is, the whole of the FSB 5th-Branch is under criminal investigation and many are under arrest for...embezzlement from the state.

Unknown to most is that for years Vladimir Putin has been placing billions of dollars into the 5th-Branch budget for the express and sole purpose of bribing Ukrainian officials, that is, military officers, Ukrainian secret service officers, Ukrainian internal security officers, and politicians. After Yanukovych was ejected in 2014, Putin got serious about bringing Ukraine back into the fold.
Here is the fun part. I am told by people I know (who are still in the game) that for years Sergey Beseda and Anatoly Bolyukh have been embezzling every dime of the bribe budget--literally billions of dollars. And everyone in the 5th-Branch was getting a piece of the action, all the way down to the field operatives who were supposed to be doing all the bribing. It was the perfect crime, spy bribes are paid in cash, and nobody, not even Vladimir Putin was crazy enough to invade Ukraine so nobody in the FSB was ever going to try to collect on the bribes that were never paid.

And this went on for years--since at least 2014.

Until, late last year.

Sometime in the October-November 2021 time-frame, Vladimir Putin called a meeting with a select few people, including Beseda and Bolyukh, and told them that Russia was going to invade Ukraine.
To have seen the look on the faces of Beseda and Bolyukh, because once again, none of the preparatory Ukrainian bribes had ever been paid. Putin had been given reports saying they had been paid, but in reality, not a penny had ever been spent on bribing--Ukrainians.
And as the story goes, Vladimir Putin was depending on--actually counting on--all these bribes having been paid. Because during the meeting, Putin discounted any resistance from Ukraine, saying all he had to do was kick on the door and the whole country would fall--in two days--because for years the FSB 5th-Branch had been doing such a good job at bribing Ukrainians.
I shi* you not.

The Russian army and air force signed off on the plan, with the assurance that the Ukrainian military was bribed and would not fight. The plan even included sending Russian police officers in the first wave of attack (to direct and control traffic in Kyiv) because according to the FSB 5th-Branch there was not going to be any resistance.

Beseda and Bolyukh (indeed the whole of the FSB 5th-Branch) now had a problem. A very big problem indeed.

What do spies do when they have a problem (that they want to keep secret from the boss) and they can`t solve all by themselves? They go talk to other spies and ask if they will help them solve their problem. And that is exactly what Sergey Beseda and Anatoly Bolyukh did.
It is well known that US intelligence (CIA) had very fine-grained, exact, precise, perfect, word-for-word intelligence on Putin`s invasion plans very early on in the game. Yep. You guessed it.

The perfect way to keep the secret about the whole FSB embezzlement scheme was to make certain there was no invasion. And the best way to make sure there was no invasion was to tell the CIA that there was going to be an invasion. And that is exactly what happened. Sergey Beseda and Anatoly Bolyukh gave it up. All of it. And kept giving it up, hoping beyond hope that once the secret was out, Vladimir Putin would call the Ukrainian invasion off.

And this is why President Biden (the CIA and MI-6) had months of advance warning and a crystal clear view into Putin`s invasion plans, the FSB 5th-Branch, almost everybody in the 5th-Branch was mainlining intelligence into CIA/MI-6 in a vain attempt to save their lives.
Sergey Beseda and Anatoly Bolyukh?

Yeah, you won`t be seeing them again.