We can’t have more than two political parties, this is one of the major failings of our first-past-the-post voting system. CGP grey has made a couple of really good videos breaking down the why of this, but the tl;dr is that FPTP voting effectively necessitates strategic voting (voting against who you don’t want rather than for who you do want).
Until we move to something better, such as ranked choice voting, we’re always going to effectively have two parties.
The UK has, for some reason, 5 different voting systems, only one of which is FPTP.