Why is there diamonds in silver right now

They could have been boosted last season. i assume you don't mean that they are currently diamond... lets take this into consideration however... If you are in a division 5, in order to be demoted into the next next lower 1 division (Plat 5 to gold 1) your mmr most be so low that you are playing against divison 4's of the lower teir. (D5 playing with P4) Lets say that someone ended the season 5 at that mmr. so even though they are diamond, they are really playing against plat mmr. after the season reset, their mmr at plat 4 if further decreased. if they were to lose 10 or 9 games in their placements, they may very well get placed in silver. Plat 4 to silver 2 isnt that much further down. I have friends who got gold when they were diamond(but with diamond mmr). So i think its reasonable actually