I would guess because it was a lot more difficult and costly to handle those threat 10 years ago.

Yeah, 10 years ago a venue receiving threats had to purchase additional insurance, hire additional security, and run a SWAT team like surveillance operation. After that became routine, every venue that can host any gathering of any size became a security sink that ate attention and distracted potential opportunities as public levels of casual violence simply skyrocketed to the levels we see today.