Different architectures scale differently with the transistor count. Clock speed for traditional desktop/server chips hasn't increased a lot over the last decade. A lot of transistors have been thrown at speculative execution to increase the effective speed by implicitly creating parallelism. Besides the security problems associated with speculative execution, this is an uphill battle. Explicit parallelism is an interesting alternative. One reason, that the Itanium failed, was that it was considered huge and power-hungry. And indeed its transistor count was high compared to the x86 chips of the time. But times have changed. The 3 billion transistors of the last-gen Itanium look almost tiny compared to the over 8 billion transistors in Apples A13.