Definition of "to lull"
calm or send to sleep, typically with soothing sounds or movements.
The expression "to lull [someone] into..." is used when you are in some sense tricked into feeling calm and OK about something, when in fact it's not something calm and OK. Almost like "luring" someone but with a less negative connotation.
Edit: Note that "to lull INTO" as in this example is slightly different from "to lull TO". For example, soft music may lull me to sleep and involves no trickery. But when someone is lulled INTO something, then some trickiness may be involved.