Almost, but plenty of computer architects speculated about vulnerabilities in speculative execution. It just seemed infeasible. The attack can differ based on the particular architecture (cache hierarchy, associativity, latency per instruction, buffer sizes...), clock speed, microcode, workloads, temperature, and a thousand other variables.

Spectre was more impressive than a new idea: it was a brilliant execution of an idea that every architect eventually had. Rowhammer was similar. Everyone knew that it was possible to get boned by physics, but it can happen at an arbitrary place in an arbitrary way that isn't captured by any model. Rowhammer wasn't impressive because it was an idea, but because it was a simple, obvious in retrospect, way to exploit physics to bypass the models.