Manafort used a russian intel asset to tamper witnesses, thats 100 on a scale of 1 to 10 of dumbness

[Perseus]

15. Correct me if I am wrong but reading about his shenanigans with Gates

I found that he was not only careless, but nor very smart, a lot of the things they did was sort of amateurish (I am no expert), but that is what the article stated. If I recall correctly, in the article the author referred to some of the paperwork that was submitted to some banks and he found a lack of detail and professionalism.

Anyway, I am not surprised he tried to tamper with witnesses, even knowing he was being watched and most probably listened to all his conversations.

They should place him on a high security jail because as someone already said, he may end up eating some fatal dessert just to protect trump, and also to make his discomfort high enough that he will want to talk and be taken out of jail. Also, do not put him in a cell with a criminal, the criminal could get an offer to do away with Manafort.