Everyone from UEFA to the clubs themselves really have made an absolute mess of things.
Multi club ownership / investment is always a potential huge conflict of interest and incredibly damaging to the integrity of any competition when those clubs are placed in a situation where they directly compete with one another.
The rule should be if the same person, fund, company or whatever has a significant holding in a club, say 5% or whatever figure you feel, then that is enough to cause conflict of interest and those clubs cannot enter the same competition - choose one and drop the other. All the talk of blind trusts, control or influence is just water muddying nonsense.
Look at Forest for example. Does anyone remotely believe that Evangelos Marinakis putting his shares into a 'blind trust' genuinely eliminates his control or influence at the club?