@Mab_813 The US isn't that much different. To do well in the primaries, a candidate needs money from big donors. So before individual voters get a chance to have any say, the big donors decide who to support.
Larry Lessig has some TED talks about this, if you'd like more information.
https://youtu.be/mw2z9lV3W1g?si=S-3-xLcFKyD0Mqef
The thing that is most bizarre about the US system is that parties aren't actually regulated, and aren't an official part of the system. Our Constitution doesn't mention them. They formed and subverted our system after it was created. At some point they stopped being about ideology and became shadow corporations that sell policy to donors, and sell tribalism to voters. Their primaries even happen at taxpayer expense, making parties look official when they just private non-profit corporations, accountable to no one.
Other countries formed their proportional representation systems after seeing the problem that parties caused in the US. But we never fixed it.