This is an open question. Anti-trust might have been a factor, but it might not have been.

First of all, IBM didn't expect to sell more than a few PCs, but wanted to have one to complete their product line - so there wouldn't really be an anti-trust angle.

Since they didn't expect to sell many they gave creating it to a low budget project with little oversight - and that's what made it a success.

Don Estridge, the guy in charge, decided to use cheap, existing third party technology and do as little expensive development as possible.

Most importantly, he looked at what made the Apple II wildly successful - an open architecture and third party participation. Basically, he cloned the Apple II with somewhat more modern components.

At the same time Steve Jobs was looking at things differently. He said, "Look at all those people making money on the Apple II. That money is rightfully Apple's. This must never happen again".

The rest, as they say, is history.