Because the engine manufacturer is American. Or do you have some recent insider info that the rules have changed?
The "rules" haven't changed at all. Mishap investigations are conducted within and by the country where the mishap occurred. It's possible that the NTSB might be invited to participate, but they have no right, nor jurisdiction. This is a matter for Kenyan authority. Where the engines were. manufactured is irrelevant.
This appears to be a case of mishandling by the crew doing the engine run; if the aircraft jumped the chocks, it should have been powered down and braking performed right away. Unless an engine ran away, it's not an engine problem. It's possible an engine manufacturer might be pulled in, but only if there's an engine problem. Neither the NTSB nor the engine manufacturer have any authority beyond whatever invitation that the Kenyan's extend.
How does a plane jump chocks?
A plane jumps the chocks when the chocks themselves weren't properly set.
An aircraft jumps chocks when the brakes aren't set. Chocks are backups for safety, but aren't what's holding the aircraft during an engine run.
I doubt any structural damage, only skin, but depending on the age of the aircraft, residual value, cost to insurers for the claim they may be repairable and back in the air sometime in a few months.
Clearly there is substantial damage, and there's clear structural damage.
What do you think of this? My idea. LOL I know expensive better than damaged or prevent injured or being explode or anything. It should install in the run up area only.
The design makes sense as providing additional resistance against movement, but there's a reason that brakes aren't put on nosewheels. In the case of the runup, wheel brakes need to be set: they're the primary means of preventing the aircraft from moving during the engine run. Mooring straps, barriers, wheel chocks, and other backups are just that. If an object is placed in front of the nosegear to hold the airplane and an engine run performed without wheel brakes set, an excess load will be placed on the nose gear.
99 to 1 they didn't set the brakes for this engine run.