So many dreadful bus crashes

We are still reeling from another dreadful fatal crash involving wedding guests up in New South Wales and now there is another bad crash involving a bus over in Canada Recently there was another bus crash involving schoolchildren. I’m wondering if it is just an awful coincidence or whether the bus drivers are overworked because of a short supply of drivers. Or is there something amiss with the buses themselves? These crashes seem to always involve multiple fatalities with buses overturning, often with no other vehicles involved.