My guess he pitied her
Okay. So he might have heard her story in the first timeline and pitied her and also made her forgot about it. Then he made it double. Also he never really explained why he was hiding that he was the actual tower mage leader whatever nameiforgot
So that's great
From vaguely remembering spoilers from the novel
It was Serena who asked him to do it the first time cos when Arinda did the mean things to her in the 1st timeline she could sense that she didnt mean it and felt bad through her emotions power, so asked him to turn back cos she wanted to know her better
And the second time was because Luke was curious about something with her .... i think
oh damn i cant wait to read this part in the manhwa. really really hope they put details in the actual manhwa and doesnt water anything down hdhdhd
ANYONE GOT SPOILERS AS TO WHY HE DID JT???