I think they have a higher mortality in countries where regular bikes are more common because the elderly use them to get back on the streets again.

In the Netherlands the introduction of ebikes (limited to 25kph) has caused a spike in bike traffic deaths because many elderly people are brittle and don't have the response times they used to have, causing dangerous situations even at relatively low speeds.

Those mortality rates only really affect the drivers of the electric bikes though. AFAIK there's no increase in deaths because of drivers hitting others. After all, an electric bike, even going at high speed, is just a silent motor bike that any driver using their mirrors should be able to detect anyway.

I think increased dead rate for the elderly largely is because they remain mobile for longer.

https://bicycledutch.wordpress.com/2020/07/28/road-fatalitie...:

“The number of people over the age of 70 was 1.5 million in 1999 while there were 2.3 million early 2019, an increase of 56%! Partially helped by e-bikes (which are not more dangerous than ordinary bicycles) this much larger group of elderly people cycles more often and further, which is unfortunately reflected in the fatality rate.”

Technological improvements that have helped increase safety of e-bicycles for the elderly are weight decrease because of battery improvements and lower centers of gravity (mid-drive electric bicycles are becoming more common). Both help decrease the number of deadly accidents not involving other traffic.

It's a lot harder to seriously injure someone with an e-bike as apposed to a car or motorcycle. Simply physics since the weight is a lot lower