
You have to keep in mind the omega was marked against his will. He rejected the alpha and the alpha came to his apartment without any notice so the omega is technically raped and bounded by force.
The omega wanted to find a mate was because he knew his heat was beyond the control of the meds and so that he will not trouble/affect anyone anymore. He knew his feelings for the Beta even before he was raped and was saddened by the fact they can never bond.

I agree with you, it doesn't make sense that after he was marked he immediately accepted the beta that he rejected for so many years and used him when it was convenient.
The omega was extremely selfish and just because he was marked without his will, he turns to the beta cause he knows he won't reject him and because no other alpha will want him now.
That's him being an opportunist.
Don't forget how he bragged about finding a sugar daddy alpha to the beta ,while he knew the beta loved him, just because he was raped.
That was his karma ╮( ̄▽ ̄)╭
I wanted the beta to find someone else worthy to be loved and fall in love with him.

He was fine with living by himself and going into heat by himself, the beta was the one who went after him during his heat. You really think he had a choice during his heat?
Also, you see during that same chapter where the beta comes during his heat at the end that he was in love with the beta, but because of his hormones he couldn't be with the beta since the beta couldn't claim him.
He bragged about wanting to find a sugar daddy, but that doesn't mean that as his friend he should tell him to go get with someone he (the omega) thinks is an asshole.
No one deserves to be raped, being raped is not karma, being abused is not karma.
(Whatever, I'm going to stop since obviously there will always be people out there who think that people who have been raped or are in an abusive relationship, deserve it.)
I didn't like the omega and felt really bad for the beta. How could you settle, get marked and for nothing? The kid was cute...But unfortunately not enough to make me like this one or forget the stupidity and selfishness of the omega. ╮( ̄▽ ̄)╭