Right, so Twitter says it was against his wishes. Oh poor lad. Feel sorry for him. How could Guinea do this to him?
He didn't even want to come off the pitch in his last match against Nigeria. But most UK didn't watch the game, nor do they know anything about African football, so this stuff is lapped up on Twitter.
In some countries (especially in Africa) the FAs are composed of shady individuals backed by shady governments. In these cases refusing a call-up or going against an FA decision leads to a national campaign against the player orchestrated by these individuals.
When you still have your family over there and would like to avoid these problems with people essentially backed by governments even shadier than they are then you just comply.
A good example is Salah last summer with the Egyptian FA. If he wasn't the absolute star that he is in Egypt and the world and was just a normal player (for example Elmohamady or Hegazi) then he would've been crushed by those people. (And they tried to crush him).
I'm not saying Keita is not to blame, but we have to take into consideration that he could've found himself in a similar situation. If not then he is to take 100% of the blame. Totally unprofessional.