Succession is interesting to me because nobody in the show knows how to express love.
I was surprised to find out that a lot of the fandom shipped them so... sincerely? I think it's been clear from the beginning that Greg is attractive as an emotional "rebound" and punching bag who can't leave. If Shiv was more reciprocal, Tom wouldn't need Greg at all.
The possessive aspect is definitely great angsty ship fodder, I just think the love triangle is even juicier. Shiv is afraid to give her heart to anyone, Tom flails in the absence of real assurance and clings to other avenues to power, and Greg, uh... wants money.