Satya Nadella wanted to make nice with longtime rival Google when he became chief executive of Microsoft almost a decade ago. Those days now feel like a distant memory.

Google’s antitrust trial in Washington, D.C., has provided a stage for Microsoft to air long-simmering grievances about the search giant’s market dominance. It also has opened a window into the events that led to a straining of relations between the two companies, a dynamic that has grown increasingly tense during the boom in artificial intelligence.