My speculative hot take on the reason that Toyota did not jump on the EV bandwagon and stuck with PHEV/Hydrogen is that much of it's operations are financed indirectly via low cost Japanese bank loans encouraged by Japanese government. These loans probably have an underlying perhaps unspoken component which nudges them toward business models which employ Japanese workers.

The one thing that EVs require is an EV charger network to exist in the foreign countries that Toyota sells the cars to. Without an existing EV charger network, it becomes a chicken and the egg problem for Toyota since, as a Japanese company, it would likely would face a difficult time getting financing to build an EV charger network in foreign countries.

Hydrogen fuel theoretically would just be an adaption of the existing petrol gas station infrastructure so the existing players/gas station networks would just need to switch over.

Now that ElectrifyAmerica is more "a thing", Toyota can start shifting strategies.

VW and US car brands could move faster since they were required (VW) and had government support (US car brands) to finance the US EV network. The Korean autos switched earlier as they were probably more hungry than the Japanese incumbents.

There's also the game theoretical play that being the only major petrol based auto producer could lead to pricing power if the transition takes longer than expected.