I take a different view.

Overhead electrification is fine where traffic volumes and power requirements are high, e.g. NE Corridor, and other high speed and/or high frequency passenger operations. So things like Caltrain (with possible future HSR use) are a good fit. Most urban rail transit is a good fit. And in those operations short branch lines that have relatively little traffic can run with battery/electric hybrid trains that recharge when on the overhead. In such operations, the expense (and it's substantial) of installation, maintenance, and power for the electrification is fully justifiable.

OTOH, US freight is almost uniquely unsuited to overhead electrification. The power demand may be there per train on selected main lines, but the operating pattern with relatively few, modestly-powered (typically the minimum needed to get it over the road, perhaps plus one unit for redundancy), low-speed trains just doesn't make sense paired with expensive overhead wire - and how much does the power cost? Then, most branch lines - the few that remain - are even less-used. Frankly, wiring the US freight rail network makes no sense; and given privately owned railroads that have to squeeze out every penny to pay the stockholders their dividends this quarter, even if it made technical or long-term financial sense it would never happen.

So freight railroads will continue to use diesel as long as they can, and when finally forced to change will probably go for an interim solution like LNG before switching to hydrogen for its support of Fast Fueling. Yes, some battery units will be in the mix to create "hybrid" consists, and in a few special cases such as switching routes in extreme air pollution areas (like Pacific Harbor Lines, doing it now) where heavy use at low speeds with regular charging opportunities favors battery over hydrogen.

As for things like Arrow: if it were not necessary to maintain connection of the line with the national railroad network (mainly, in Arrow's case, to allow running a couple of regular Metrolink trains a day during peak hours, for one-seat rides to downtown LA, though there is still a little freight traffic), it probably would have been a candidate for overhead wired light rail. That's a standard enough thing that the cost is reasonable and predictable. It's not practical to wire it, though, unless and until Metrolink wires the San Bernardino line connecting with it - something that probably won't happen in us geezers' lifetimes. Hydrogen-fuel cell FLiRTs are a catalog item, though, even if in vanishingly small production volume, so with the modest amount of traffic on Arrow it's reasonable to use it there.

Note that Caltrain wanted to do electrification for a long time, and considered it necessary to deal with rising diesel fuel costs that threatened the viability of the line. They did a lot of planning and paperwork for it over the years. But they couldn't actually get started until HSR provided a big financial boost. It's expensive to convert. One plus side is that they got it done about the time demand patterns changed dramatically after Covid, making it more like a regular transit operation than just commuters. Electric is much better than diesel for that kind of operation.