As I understand it (others please help) in a parliamentary system with many parties, the parties each tend to vote as groups. (Dems do it here, Republicans not so much. See Romney, Collins, Murkowski). I think its quite formalized.
So if one party, like Likud, doesn’t get a majority by itself, it asks another party to join in, so that they have a majority together. IIRC, there is an ultra-orthodox party that has quite a bit of power disproportionate to the number of seats they hold because they often ally with Likud to form a coalition. Of course, there are agreements and concessions, so the parties to the coalition know what to expect from the new government.
There’s party discipline because there is a list made by party leaders of who will represent the party in the Knesset. There’s no geographical districts that can impose a disloyal member on a party.