Why was Nadezya Ostapchuk sentenced just to one-year suspension?

The Belarusian shot putter Nadezya Ostapchuk received the gold medal at the 2012 Summer Olympics. But she failed a drug test. As a result, she forfeited the medal that was given to Valeria Adams of New Zealand.
Two tests manifested that a steroid’s metabolites presented in her urine samples.
If an athlete is caught applying any prohibited medicines, he/she is usually sentenced to a suspension of two years. When it comes to this Belarusian shot putter, she received one-year ban. Why was the sentence lighter? There were several circumstances that proved the following condition: the shop putter didn’t take any forbidden product knowingly.
At the beginning the shot putter blamed his former coach. She confirmed that he had sabotaged her sample.
The Belarusian National Anti-Doping Agency examined this case. The International Association of Athletic Federation also participated in the investigation. It was defined that Yefimov was guilty. This person put powder of methenolone into food of the Belarusian shot putter during the last week before the 2012 London Olympics. The coach affirmed that he had worried about Nadezya Ostapchuk. He thought that this steroid would help to win.
Actually, it is difficult to determine why Yefimov has done it. He only made the things worse.
Anti-doping agencies accepted these statements. That’s why Nadezya Ostapchuk received just one-year ban.
As for supporters of Valeria Adams, they didn’t believe that Nadezya Ostapchuk had not taken the steroid intentionally. They claimed that Yefimov just tried to protect Nadezya Ostapchuk. They confirmed that Nadezya Ostapchuk had taken steroids under recommendations of her coach.
If Nadezya Ostapchuk’s performance was amazing certain months before the 2012 Olympics, her coach had to be sure that she would win. Why did he trouble about?