Ask HN: Why do big companies tend to only build with Java? 15 years ago
1) Corporations don't understand IT. To them it's a cost center, not an enabler. So to minimize costs they must find developers that are (a) easily replaceable (b) cheap to hire
2) Sun did a great job marketing Java in the late 90s and early 2000s. So corporate managers felt safe adopting Java; it was the "in" thing. And as kls said, corporations have a lot of inertia. Why break something when it's working? (It's due to this mentality that some corporations still run VB6 and COBOL apps)