How bookmakers manipulate odds — delaying the bet

So here’s something that’s been bugging me. Last month I was tracking odds for a Europa League match, and the line moved in such a weird way. I noticed the underdog had better odds early on, and then the market slowly shifted toward them throughout the week — almost like the bookies “knew” people would start betting late. I ended up hesitating, thinking maybe I'd get a better number later, but by the time I decided to place the bet, the value was gone. Do you think this kind of movement is just natural or do bookmakers really tweak the odds to push people into betting at bad times?