We also have more than 2 parties in Spain, however the way votes are counted it’s better to vote for the big parties than the local ones. Literally, voting your local party and them supporting the big “left” party will amount less seats than just voting the big party. Usually people vote locally but since we have the looming danger of the extreme right party, people have been focusing on the big left, just to ensure that we don’t get Vox.
Still having more than 2 parties promotes discussion and makes it really difficult for a party to go rogue.