Dr. Soong underlines that the Androids are 100% identical in hardware and have only a "slight" difference in programming. Then when Lore gets the emotion chip suddenly "those circuits" were NOT compatible to him and only properly working with Data. I find that "odd".
A slight difference in programming that created a maniac vs a well adjusted being
I too echo the sentiment that Lore's programming was simply not designed to additionally have Data's emotion chip programming together. Obviously the tech was compatible. Data & Lore are compatible with almost all the tech we ever see on the show. Riker hooks his head up to the warp core in Disaster, for god sake
The concern was that Lore was not programmed to have Data's emotion programming. He already had some kind of oversight in his own, that Soong never got around to fixing, because he thought him inactive. Sadly, I suspect he could have helped Lore, but the result of combining the emotion programs was that he murdered Soong, which seemed even too much malice for Lore himself earlier in the episode when he showed distress at the idea of Soong dying.
I always felt the original problem with Lore was that he was made "Too Good". He had better strength than a person, & better intelligence, & at least the way I see it in Spiner's performance, his emotions are stronger than a Human's too. He is carried away by them. Thus why he can be mad a Soong one minute & then in a flash, be distressed to find out Soong is dying. He's overly emotional on a dangerous scale
This is why I don't hate "Descent" as much as most people, because even though it might be a paltry development for the Borg, it was a fairly crafty evolution of Lore, post-emotion chip. It turned him from just a overly emotional genius into a ruthless megalomaniac, hellbent on ruling the Galaxy, & with Data under his control, I believe he could have succeeded