1) Founder/cofounders
2) investors
3) people who do not work at the company and are not investors that people in groups 1 and 2 think will be on their side during important votes
In the UK corporate governance code it is quite clear that a board should have an exec CEO and a non exec chair. The chair runs the board the CEO runs the company. The board oversees the CEO. It would be extraordinary (and pointless) not to have some execs on the board.
And it would be extraordinary and pointless if the board members were all employees, it has a separate function of supervision and thus is usually mostly non-employees outside the CEOs chain of command.
2) not true in this case. Two of the people on my list are execs