Apple was failing as computer company. Apple only survived because Microsoft threw them a lifeline, licensing Office suite in Macs and investing in Apple. Microsoft wanted to show anti-trust regulators that there was software competition in PC market. If there was no anti-trust suit against Microsoft, Apple would have likely went bankrupt.
Microsoft was on the way to owning Desktop and web space, by tightly integrating IE into Windows. Left on own, Microsoft would have routed all default browser traffic to Microsoft search engine on MSN. Google would have remained some student research prototype into an algorithm about backlinks.