Professor_Genki

it could be a "planted in creation" line of thought, to be able to more easily sway them into the fold.

Ferrus once comented about the replacement of body parts for bionics present in his legion. So kinda, they did not go as fanatical as after the heresy but it was there.

Ferrus Manus The Gorgon.

emperor chose not to influence the belief of the mechanicus, because it would create conflict and it was deemed not worth it.

also, the assassinorum

they are astartes, to kill a corrupt governor is nothing.

and not lose on man power that could be spared to die another day.

while he probably could have done it, he chose not to so he could start the crusade earlier.

the emperor did not influence the belief of the machine cult (later mechanicus) because as he as starting the crusade he did not have the time or resources to deal with them in a worthwile manner