From what I understand, drivers are told to beware if someone is coming up behind them on a flying lap, and drivers also have an understanding not to go flat out, on an out lap when approaching other cars from behind. So Hamilton wasn't expecting what happened, particularly with the Williams.
With the Ferrari, he wasn't sure which way Kimi wanted to go and wasn't sure what to do apparently.
As for Vettel, he should have been disqualified from the weekend on the spot. All drivers know the routine when the computer randomly calls them to the weighbridge.
He should have immediately switched off his engine, but yet again his arrogance decided that he was in a big hurry, so the rules needn't apply to him. The guy at the front was constantly signalling him to cut his engine but he wouldn't do it.
The car couldn't be weighed accurately because his engine was running, so its eligibility to compete couldn't be ascertained, therefore it should have been immediately excluded.
He then proceeded to destroy the pads on the weighing device when he drove off them, thus meaning no other cars could be weighed afterwards.
If this was accidental then I suppose the fine imposed could be punishment enough for that.
A conspiracy theorist might suggest though the Ferraris were running under weight and didn't want to be weighed.
The very least that should have happened was that the Ferraris weren't allowed to take any further part until they had been weighed.
If that wasn't possible due to Vettel wrecking the weighing device, then that would have been their own fault.
I suspect they might nick the race due to their tyre tactics during qualifying, but you can never rule Hamilton out as long as he isn't at a huge disadvantage.
The first corner might be very interesting.