They did what they were told and didnt argue.
Same as Hugo Boss made SS uniforms, a lot of german people and companies at the time just went along. Even if they didnt wholeheartedly swallow the propaganda, even if they quietly hated the Nazi regime, they saw those that spoke out beaten, killed or straight up vanish. Some of the companies willingly stuck their heads in the sand and just went along because they knew that to resist was to mark yourself, and to cooperate was to profit.
There is a book about it: IBM and the holocaust.
here is a summary, hopefully not paywalled.
Didnt realise you were asking specifically about IBM. IBM definitely knew they were doing something wrong.
Yeah,This article should give you a good outline.