No, it was only because of power density i.e. too much heat dissipated in a really small area. There is no way to "solve" this issue, other than to just throw more cooling at it. And since more cooling = more money, Intel (and friends) went down the multicore route instead.

No amount of R&D spending can bend the laws of physics to overcome the inherent limitations of silicon. I'm sure Intel also looked into alternative semiconductors (e.g., III-V) before giving up on the 10 GHz dream.