I can only guess.
I reside in Australia. I have purchased online locally (inside my State), Interstate & International throughout 2020 & 2021.
There's probably limited airfreight services being allowed into and out of countries along the route. Those freighters that do fly would charge those packing their parcels onboard, a bit more to pay for the expediency.
Also, I did notice one parcel went through USA & over the Pacific to get to me from EU. Usually that box would've gone in the other direction, through Singapore & then down here to Australia.
I think we have to assume that all the international Freighters have to weave their way through a myriad of COVID restrictions which inevitably brings on delays and probably increases cost. Crews may have to be quarantined upon arriving at terminus destination, at operators expense, for example. If crews are being quarantined that means they are out of action for the return flight, so another crew has to be engaged to do that the next day? That sort of logistical nightmare must drive costs up.