The points:

1. Just because you madly love one person, doesn’t equate, logically, that you cannot madly love another person. What I am saying here: the condition, “madly falling in love with someone,” isn’t restricted to one person.
2. To expand that point, polyamorphus people so exist and often have multiple lovers. This is different from, say, polygamy as polyamorphus means not multiple wifes but multiple lovers.
3. Going even further, people can find two people that they ideally love and can often struggle to just stick to one love-interest. I don’t need to recall highschool, uni/college or middle school, now do I?
4. Often with breakups, people do get seperated and, rarely, get back together. So the need to feel loved is very strong yet repressed at the same time. Yet in rare cases, people who do “mentally heal” from the event can often love, once again, who they broke up while loving another person as well. Joy is a miracle drug.
5. The concepts of multiple partners runs it way down back to antiquity - I do not need to speak of sexual activities, but certainly if they were willing to go that far they ought to have a baseline love of each other and trust at the same time.
6. To bring it into contemporary times, the Sexual Revolution of ‘68 goes to show that multiple partners in a relationship can work - doesn’t mean it has to be that way for long.
7. Which that tradition in antiquity follows us even to today with LGBTQIA+ communities that certainly does have polyamorphic people in its fray.
8. To make a final pitstop in theoriticals, love, whether “a chem reaction” or a real thing, is subjectivised heavily by a person. How they view how they can best deal with love and find corresponding/complementing partners that shares that vision should be taken into consideration. As such, it shouldn’t be surprising polyamorphic relations do sprout out in society.