Two reasons Hitler killed Rohm.
The industrialists, whom Hitler needed to build the war machine, did not like Rohm and the SA, because they called for complete nationalization of all German industry and the liquidation of the industrialists.
The Wehrmacht would not support Hitler, because Rohm wanted to replace them with the SA.
Hitler could never gain power without the support of those two main constituents.
It was strictly business.
“It was strictly business.”
Bingo. Roehm was basically a true Communist rather than a fascist. He had to go.