IBM didnt need any suggestions from Bills mother to talk to Microsoft, as Microsoft was IBMs first choice due to Microsofts public reputation as a leader in microcomputer software.
CPM was eventually produced for the IBM, but long after Gates produced DOS, and it was produced as an aftermarket product.
If Digital Research would not have blown off, and pissed off, IBM, Microsoft would not have produced DOS.
At the time, Microsoft was actually producing XENIX, an AT&T UNIX product. During the early 80's, many people at Microsoft wanted to focus on the UNIX market.
Imagine the world today if that had happened. CPM was good, but its useful life, like DOS, was limited. UNIX has an indefinite useful life. We also most likely would not have seen Windows NT, lawsuits from Apple, Linux, etc.
Microsoft would no doubt still be big, and who knows how big. Imagine if they could have concentrated on things other than DOS, which REALLY held them back, IMHO.