Again, that is because no one ever found any 'manifestos' claiming Obama as inspirational of inciteful for any of the shootings. Not one of them.
The racial divide was stoked by the morons who pushed the birther conspiracy and who made it clear that they resented and feared Obama presidentin' while black.
Identify the disaster that the prior administration strangled Trump with.
No one ever blamed Obama for ANY of the mass shootings when he was President, even though he stoked the racial divide in this country more than any President in the history of the office.