It is always a surprise when a public figure wins a defamation case in the US given the different approach they take to such cases compared to the UK. The jury in the US had a lot more evidence to consider than the judge in the UK (I'll say more about that below) and it was clear that Depp's lawyers had moved the needle significantly in his favour, but the outcome was by no means guaranteed.
My view is that it is clear that Heard abused Depp. Given the evidence, I think this is beyond doubt. Whether Depp abused Heard is a more difficult question. The evidence is a lot less clear. My view is that there is enough evidence to show that many of the incidents claimed by Heard did not happen, but I can't say for sure that he never abused her.
We will probably hear from the jurors in the coming days, but I suspect the main thing that swung them towards Depp was the fact that so much of Heard's testimony was exposed as lies. They may also have considered the fact that, apart from her sister, Heard was supported entirely by paid witnesses (experts and people on her payroll), whereas Depp was supported by a number of witnesses who were not on his payroll and the attempts by Heard's lawyers to discredit them as Depp fans and/or liars failed. However, that is just me guessing. I will be interested to hear what the jurors say if they talk to the press.
It appears that Heard intends to appeal, so this may not be over yet.
Of course, in the UK it is still safe to call Depp a wifebeater based on the decision in the UK case. We will never know if the judge would have arrived at the same decision if he had seen all the evidence that was presented in the US. In the UK case, because Depp was suing NGN rather than Heard, she was not required to disclose evidence that was damaging to her case - evidence that was included in the US case. Also, in the UK each side presents its evidence and that is it, so Depp did not have any opportunity to rebut claims that Heard made in court that were not included in her witness statements. In the US, Depp was able to put forward rebuttal witnesses after Heard's case (and she was then able to attempt to rebut his rebuttal). This allowed, for example, Kate Moss to deny Heard's claim that she had been pushed down stairs by Depp, the trailer park manager to deny the claim that Depp had caused thousands of dollars worth of damage to the trailer, and the ex-TMZ employee to undermine her claims that neither she nor anyone on her team had leaked the kitchen video to TMZ or given TMZ any tip offs.