Because Obama never posted himself as Jesus unlike Trump who does it without remorse.
The more people who continue to defend Trump's words just reveal that they worship/idolize him more than Jesus. This administration desensitizes you to blasphemy and you can't live without it.
That obama photo is cherry-picked from a thumbnail of a video made in 2014, not 2016, by a person criticizing obama. The president or anyone near him did not endorse this. This user is spouting bullshit.