Basically, they were so worried about secrecy of their trading algorithms and people sharing them with other companies

Which means if you took the job they probably would have had you sign some obscene non-complete/non-solicit/non-disparage/non-roll-your-eyes-at-them agreement. Despite the dubious enforceability of these, especially in some jurisdictions, you would still likely experience a lot of stress and expense (i.e. lawyer-up) if your departure rubbed someone the wrong way. Your exit from the trading world could involve:

  - demands to keep them informed of what you were doing
  - private investigators checking in on what you are doing
  - threatening legal letters
  - or actually being sued

And that's if you did your very best to follow the non-compete agreement. If you were actually taking employment in a field remotely related to finance, you could have the DOJ/FBI knocking on your door to investigate trade-secrete theft.

EDIT: And another point about "double the comp". The comp structured so that 75% is a discretionary annual bonus payout (with claw backs), and your base salary is 25%. So you could actually end up making less money, depending on the whims of the markets and/or internal politics.