I think the big driver for solar inverters was panel cost reductions. With motor drives it's straightforward even 25 years ago to see the benefits and applications of slapping a DSP and some digitizing sensors onto the system to do crazy control stuff. But PV cost was just way too high for this stuff to have tons of active research until recently. Once panels got commodized, the industry pretty quickly noticed how much virtually free compute is available, and moved to fill the gap. It's certainly been interesting watching commercial PV inverter design start with an extra decade of compute improvements and cost reductions as the industry effectively speedruns the design challenges - even with only a few active research projects before 2015, we've had designs in hand for a decade and no scalable way to deploy them.

The commoditization of computing power, and the continuous decades of improvement in digital hardware performance per watt, has reduced numerous classes of analog problems to an exercise in fast enough bit-twiddling. I think in motor drives the big jump to simple hardware and beefy controller was directly downstream of the creation of usable 32-bit motor controller DSPs, along with software toolchains that made it possible to compile optimized C and C++ libraries for these architectures. Up to early 00's there just wasn't enough real-time computing power available for most of the market to take advantage of it, and what little did exist wasn't directly targeted at motor drives. But it is worth pointing out that the S-curve of digital adoption probably got started as far back as the mid-90s; the only people who could really take advantage of it back then were at the cutting edge with very expensive low-volume projects. I'm sure it felt like an overnight event, but it took a decade for motor drive DSPs and software toolchains to get good enough that most people felt compelled to switch.

ETA: oh gosh I forgot FPGAs happened then too, that probably had a lot more to do with it... Ah well, fun trip down memory lane :)

It's been very interesting watching as the compute gets cheap enough that we can start embedding it into the analog chips. The telecom chips all have DSPs in the ADCs and DACs and digital PLLs in the line cards, the battery management ICs all have microcontrollers for charge management and safety, you can buy radar ASICs for automotive proximity detection, there's gate drivers for SiC FETs in automotive traction inverters that incorporate redundant microcontrollers to do monitoring and fault detection/recovery for ASIL D compliance. So I'd add: the same way that software drives the marginal cost of complex math to near-zero, advances in digital circuitry and ease of incorporation into other analog designs drives the marginal cost of complex application requirements down. It's not quite as stark as software, but it's amazing how much quicker a single complex chip design becomes when you can digitize a subclass of the problems and solve them in real-time at virtually no cost on analog ASICs with built-in CPUs and DSPs. Analog hardware advances are extremely challenging by comparison, and can take years of R&D across a wide array of reliability and performance assessments before they become realized in designs.