As stated in the article - "the merger talks unravelled in a little more than a month due to Nissan's pride and insufficient alarm about its predicament"
More critically, Japanese automakers have always tried to diversify away from Japan as part of the "Flying Geese" paradigm.
For example, Toyota and Honda truly became "American", Mitsubishi truly became "Southeast Asian" (Indonesia, Philippines, Thailand, Vietnam), Isuzu became "Thai", and Suzuki became "Indian".
Nissan on the other hand tried a foreign expansion with the Datsun in the 1960s-80s, but that crashed and burned horribly, and reduced their appetite to expand abroad.
Post-Datsun, most of their international expansion tied their future to Brazil, China, and India as part of the Renault-Nissan partnership under Carlos Ghosn, but that itself came very late (early 2000s) and other players (domestic, international, and Japanese) were well established in those markets already.
Furthermore, Nissan Group's prestige division Nissan Shatai is too entwined politically to Kyushu, which scuttled the merger as Honda would have shut down Nissan's Kyushu factories which represent much of Nissan's capex.
Fundamentally, Nissan's leadership has a low appetite of taking risks abroad after the failure of Datsun, and this would have been toxic for an internationally minded Japanese firm like Honda who has stronger PMF abroad compared to domestically in Japan.