From what I understood he was initially trying to gain rank and appeal from Lusamine by trying to obtain an Ultra Beast, this is why he secretly did all the Ultra Beast and Type: Null research at Aether which ultimately resulted in the accident with Lillie. Once it started to look like Lillie's memories might come back, something Faba concluded from seeing Lillie was starting to touch pokémon again, he got desperate and tried to cover up by taking Lillie and trying to use Hypno to erase her memories again. And then once Lusamine found out the history with Lillie he desperately tried to go back to his original plan, hoping to gain favour again with Lusamine if he could provide her with an Ultra Beast. Lusamine obviously didn't want him around anymore after what had happened, so he had to use Nebby and Burnet's research to force the situation in his favour. I wouldn't say he's just evil for the sake of it. He's definitely not a good guy, he's arrogant and selfish and puts his own career above all else, but he has his reasons.
Anyway, I liked this episode. While the action wasn't as epic as I hoped, there were some amazing character moments. I loved Lillie's speech to her mother and how she managed to get through to her. Also love how the 10,000,000 Volts Thunderbolt looked like, and the Catastrowlet move was awesome. I'm not a big fan of the Z-pose for 10,000,000 Volts Thunderbolt though. I know they use the same as the games, but it doesn't feel like an actual Z-pose, it doesn't have the same elegance and finesse, and the poses are one of the things that, at least to me, have to be there for Z-Moves, they're what make Z-Moves Z-Moves. Also noticed that Gladion doesn't seem to use the Rock Z-Pose when using Continental Crush, he does something else. I know Kiawe fits a bit of extra moves at the end of his Inferno Overdrive, but the original pose is also still there. But Gladion doesn't have that, and I miss it. He still looks awesome and his pose is gorgeously animated, but I don't understand why his pose is different. It's something I also noticed in SM27.