I don't think this was the cause. Advanced simulation capabilities have existed for many decades in the industry. Many if not most of those tools are not publicly available.

I think there is also a distinction to be made between offline (engineering) and onboard computing resources. While onboard computers have been constrained in the past, control algorithms are typically simple to implement. Most of the heavy lifting (design & optimization of algorithms) is done in the R&D phase using HPC equipment.