How do you know?
How do you know? You don’t know! So, stop pretending you do.
Stop pretending you know what everything happens for, because you don’t. You may never know.
But you have to trust that whatever happens is happening to teach you something in a positive way, or to serve you in a positive way.
If you don’t go into that attitude, you will only get a negative result.
If you define something as not belonging, if you define automatically as negative — you will only get a debilitating result; you will not understand what debilitation might be for.
So, stop trying to know what everything is for and you’ll have much happier life. There is a pumper sticker on your planet that sums it all up: “Ever since I gave up hope, I feel much better.”