I think this is a recent development and it is mostly older people who would previously not cycle as much anymore, but now drive e-bikes and so are going a lot faster while being physically more fragile. I think they were mostly one sided incidents (them driving into stuff or slipping).

For those people, I’d indeed recommend or mandate a helmet.

Do consider that in the Netherlands, people cycle 15,000,000,000 kilometers per year (that’s over 800 km per year per citizen, including babies etc.) to put the 50,000 injuries into perspective.

(Dutch source: https://www.fietsersbond.nl/ons-werk/mobiliteit/fietsen-cijf...)