Why was china accused of cyber-attack on Microsoft?

News has came out that UK, UN and EU has accused China of a cycber attack on Microsoft.

 United Kingdom, United States and European Union accused China of carring out a major cycber attack on Microsoft earlier this year. Earlier this year Microsoft also accused China was accused of Cyber Mail attack in March 2021. The attack effecting atleat 30,000 organisations, yah you read right '30,000 organisation', it was a attack on Microsoft Exchange's server. While UK  Chinese state-backed actors were responsible and also said that the attack was likely to enable large-scale espionage, including the acquisition of personal information and intellectual property, while the EU said the attack came from "the territory of China". In a statement, the White House said it was "deeply concerned" that China had "fostered an intelligence enterprise that includes contract hackers who also conduct unsanctioned cyber-operations worldwide, including for their own personal profit". The Chinese Ministry of State Security (MSS) was also accused of wider espionage activity and a broader pattern of "reckless" behaviour. Microsoft announced details of the hack back in March, and said a China-linked group called Hafnium was responsible. China denied those accusations. Despite the strong statements, there are no signs of sanctions against China. In contrast, new sanctions were placed on Russia for the recent SolarWinds campaign which many experts believe was less serious than the Microsoft Exchange campaign linked to China. Thankyou for reading