I myself am not quite sure about the reason for their marriage, but I do know that it wasn't a PROPER marriage 😕.
In the end we had an EXTREMELY happy ending, in which the four of them meet their mom, and everyone lives happily ever after, that is, Aziz-Devika, Milind-Radha, Araina-Raunak, and of course, Prateeksha-Shashank. But it still wasn't a proper ending.
I'm sorry, I suck at analysing 😔. Let's both of us wait for someone who can tell the story properly 😃