How did Sutekh’s Trap Work?

I know this has probably been discussed (or hasn’t because it’s obvious to everyone except me), but help me out here…

How did the Doctor / Ruby / Unit’s actions in the Time Window help Sutekh?

Was that part of his trap that he needed to enact his plan, or was it just a way for the characters to discover his presence just before he revealed himself?

There’s a lot of mentions of memory being time and what is the memory of a Time Machine, but the writing isn’t the best here.