How do you strike the balance between investing in buzzy tech for tech's sake vs tech that is strategically valuable/critical?

It's really hard to know a priori. Eg the architectural concept of the network PC was clearly recognized as important in the 90s, but it didn't materialize in a successful way until 15 years later as the Chromebook.

Same for Java's write once, run anywhere. Java failed at that but the concept was successfully realized in Ajax web apps. Betting on Java would have been the wrong answer but I imagine that was far from obvious at the time.