I have no grand opinion about Trump. He is as good as any other politician, though he might be marginally better from the prior that he is not a career politician and from the posterior conditioned by the fact that the bi-partisan establishment and the corporate media hate him. These are too strong a signal to ignore.
What irks me is the cheap virtue signalling by the laptop class which has been told to hate him since 2016. They had no opinion of the man - who is a literal Hitler and who was 70 years old in 2016 - before that. I despise such fakery.
Because i have worked with many math phds who lost their youth to something that they could not make a living on (research positions at universities are few and the competition is intense) and were writing C++ implementations of derivatives pricing models for a (comfortable) living.
I am not trying to discourage you, just a different perspective.
I hope you have decent source of secondary income or your family is reasonably well off.
A math PhD might take 6-7 years to complete and I hope that, at the end of it all, you won’t have to come to London to look for C++ or Ocaml jobs at hedge funds or banks.
PhD now is an expensive way to signal that you can persevere longer than the average human.
Unfortunately, that is not always a positive as many real life situations require you to make decisions under extreme paucity of information and reverse or change course at short notice. For such professions and roles it is a liability.