Why did Nadezya Ostapchuk receive just one-year ban?

Nadezya Ostapchuk, a Belarusian shot putter, received the gold medal at the 2012 Olympic Games. But she tested positive for a steroid. As a result, she forfeited the medal that was given to Valeria Adams of New Zealand.
Two tests indicated presence of a steroid’s metabolites in her urine samples.
When an athlete is caught applying any banned medications, he/she is usually sentenced to a suspension of two years. As for Nadezya Ostapchuk, she received one-year suspension. Why was the sentence lighter? There were several circumstances that proved the following condition: Nadezya Ostapchuk didn’t use any banned product knowingly.
At the beginning the shot putter blamed his former coach. She said 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 shot putter during the last week before the 2012 Olympics. The coach reported that he had worried about Nadezya Ostapchuk. He believed that this steroid would help to win.
Actually, it is difficult to define why Yefimov has done it. He just caused the trouble.
Anti-doping officials accepted these statements. That’s why Nadezya Ostapchuk received just one-year ban.
As for supporters of Valeria Adams, they didn’t believe that the Belarusian shot putter had not used the steroid knowingly. They affirmed that Yefimov just tried to protect the shot putter. They affirmed that Nadezya Ostapchuk had taken steroids under recommendations of her coach.
If Nadezya Ostapchuk’s performance was great some months before the 2012 Olympics, her trainer had to be sure that she would win. Why did he worry about her performance?