Until April of this year, it was possible for a foreign national to be resident but not domiciled in the UK. Any income they earned in the UK would be subject to UK tax, but income earned abroad would not be. These non-domiciled foreign nationals could "live" in Dubai (or any other country) for tax purposes, but actually live in the UK in every practical sense.
The removal of this non-domiciled status is clearly far more significant than a normal tax increase. The UK was a uniquely attractive destination for the super-rich, because they could enjoy all the amenities of living in London with no real concerns about the tax implications. It is plausible that many of those people will decide to pay UK tax rather than move abroad, but we are talking about an exceptionally highly-mobile group who have already made the decision to move country, many primarily or solely for tax reasons.
The removal of this non-domiciled status is clearly far more significant than a normal tax increase. The UK was a uniquely attractive destination for the super-rich, because they could enjoy all the amenities of living in London with no real concerns about the tax implications. It is plausible that many of those people will decide to pay UK tax rather than move abroad, but we are talking about an exceptionally highly-mobile group who have already made the decision to move country, many primarily or solely for tax reasons.