Shares aren’t necessarily synonymous with voting shares nor is there necessarily a 1:1 vote to share ratio. Someone can hold 75% of the total equity in a company but if someone else owns preferred shares that give them 1000 votes per share, then that person will have more voting power than the person who owns 75% of the company. In that case then yes, the person with the voting super majority could fire the person who has 75% of the total equity.

Elizabeth Holmes owned 51% of the equity in Theranos but her voting power was pretty much 100% because her class of shares gave 100 votes per share whereas everyone else's only gave them 1 vote.

It all depends on share structure.