Why did Shakib suddenly announce his retirement?

In a bombshell press conference on Thursday, Bangladesh ace all-rounder Shakib Al Hasan said that he had informed the Bangladesh Cricket Board (BCB) that the upcoming South Africa Test series at home in October-November will be the last Test series of his career.
Following the fall of the Awami League government, of which he was an MP, Shakib has not returned to the country. He feels that if he can head back to the country and leave on his own terms, he will play the series against South Africa, which is to be his last Test series.

It is not just Test cricket that Shakib is set to leave as he further informed that he will not be playing T20 format for the next few series as he feels it is time to move on from the format.
 
Asked if he would play the T20I series against India, starting on October 6, he informed that he feels he has already played his last T20I.
“I think I have played my last match at the World Cup [against Afghanistan],” he added. 
When asked if the Champions Trophy in 2025 would be his last foray in the ODI format, he simply said “I hope so. Nine more ODIs.”