What mechanism causes solar power deaths?

Apart from the deaths from workers falling off the roof or from wind turbine towers (though these might be the only type of deaths included in these figures):

If mining deaths are included, coal, oil, gas and uranium probably do not look favorable at all, but renewables aren't perfectly safe either: there was a bridge collapse at a copper/cobalt mine in Congo two months ago that killed 32. Solar and wind use more copper per energy unit than other technologies, and solar and wind indirectly require battery technology. Lithium batteries contain lithium and cobalt. (Lithium mining seems relative safe, but 70% of cobalt is mined in Congo, which is known for artisanal mining, and the above-mentioned accident indeed seemed to happen at such a mine.) Wind, especially off-shore wind uses more concrete and steel than other power generation technologies (hydro seems like it'd use a lot too?), which could be explored too. (Course, these metals are recyclable, so you only mine them once.)

Battery factories also produce deaths sometimes, e.g. recently https://en.wikipedia.org/wiki/Hwaseong_battery_factory_fire, and batteries in operation as well as discarded batteries sometimes produce deaths too.

Accidents, mainly. Solar panels and wind turbines produce far less energy per module than nuclear, so you have to build much more of them. If you build enough of something, the odds that everything goes perfect every single time are quite low.