As the others have said; RNG is a pain!
Something else you can check..
The valheim console actually shows when it rolls to see if a random event will happen. Heres what the output looks like.

04/28/2023 09:18:17: Possible events:0
04/28/2023 10:50:24: Possible events:0
04/28/2023 11:36:29: Possible events:1
04/28/2023 11:36:29: Random event set:army_theelder
04/28/2023 12:22:31: Possible events:0

So, every 45 minutes the game "looks" to see if any player is in a region which is eligible for an event. The game looks at a combination of factors, including the presence of certain items like the workbench and beds. After that, the game looks at the player and what monsters they have killed to determine what event they can trigger.

For example, a newbie can play on a server with all bosses turned in. The newbie will not trigger any hard events because they are not eligible to trigger them. However, if a veteran player is also around; then the veteran player can trigger the hard events, even if the newbie is there.

I've noticed this while playing on my dedicated server; my novice characters only trigger the forest is moving event; while my other characters can trigger much more intense events. So, it is not only the state of the server; but also the state of each character.