From what I can tell, the jury is still out on possible causes for the outage. However, for people pointing out the issues involved in decreasing inertial stability, it is possible to convert older gas and coal fired plant generators into synchronous condensers to maintain inertial stability.
https://ancillary-proxy.atarimworker.io?url=https%3A%2F%2Fspectrum.ieee.org%2Fzomb...
"Repurposing old power-plant generators is part of a larger comeback story for a technology that seemed doomed with the advent of solid-state controllers in the 1970s. Thyristor-based static VAR compensators (SVCs) quickly conquered the market for dynamic voltage support because they produced VARs more cheaply and efficiently than synchronous condensers.
Their predecessors started making a comeback a decade ago, however, thanks to faster control systems and a growing recognition that spinning machines offered some crucial advantages over electronics. Those pros stem from a spinning rotorâ(TM)s mechanical and electromagnetic inertia, which make the machines more tolerant of grid disturbances.
Severe voltage drops, for example, hobble SVCs, whose reactive power output drops at double the rate of line voltage. In contrast, a synchronous condenserâ(TM)s spinning rotor keeps on pumping out reactive power. It will also generate real power if needed, moderating the drop in AC frequency that would result, say, from shutting down a power plant."
"Speed was a critical factor in the California Independent System Operatorâ(TM)s decision to order a condenser conversion, though in a gas-fired plant instead of a coal plant, following the shuttering in 2012 of the San Onofre nuclear power plant. Without the 2,200-MW plant, located between Los Angeles and San Diego, voltage control weakened all across Southern California. âoeThe potential for rolling blackouts in the L.A. basin was seen as a very high risk,â says Chris Davidson, an electrical solutions business-Âdevelopment director for Siemens, which did the conversion."