Hi hiutsuri
Sorry to hear you have been finding dead hedgehogs. So sad.
It’s impossible to give any reliable reason for their deaths with the small amount of information we can get here on Hedgehog Street Forum. You might like to check out this link and possibly report the deaths via that.
https://www.hedgehogstreet.org/help-ive-found-a-dead-hedgehog/
I would just say, though, that just because you aren’t in the country doesn’t mean that it’s impossible that there are badgers around. These days, I believe it is becoming more likely.
If it was a strimmer injury it’s likely that part of the area of spines would be shaved off and if it was enough to kill the hedgehog, it’s likely that there would be a noticeable injury.