On the use of the word “thief” in Imagine Dragons' “Thief”

Question

The chorus of Imagine Dragons' "Thief" (from the deluxe version of the album Smoke + Mirrors), written by Clare Reynolds and Natalie Maree Dunn, goes like this:

So take me back
When I believed
Back when I was unafraid
Just like a thief
And all the heights
That I could reach
Back when I was unafraid
Just like a thief

(Spotify, lyrics)

These lyrics confuse me slightly. Invoking the "thief," I'm pretty sure, cannot be only for the purpose of creating an example of someone who's unafraid -- why not "hero," or any other person who is unafraid? (The word is also the title of the song, perhaps hinting at something...more?)

Additionally, the word "thief" can carry a negative connotation, and so (at least for me) distracts from the request to "take me back" to an earlier, simpler, and more naive time "when I believed." Also, "all the heights/that I could reach" make more sense when connected to almost any other profession that requires bravery from its practitioners.

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My understanding of the song is that the singer is speaking to someone who doesn't understand the darkness that can exist in the world, for people who experienced things than the listener had not, as in the first stanza:

If only you
You could see
The darkest place that you could be
Oh maybe then you'd understand
From desert heat to cobbled streets
From broken home to the city beat
There's so much more than you could know

This is followed immediately by the chorus: "So take me back..." I interpret this as a hope or prayer that the singer can go back to a simpler time, so that he and the listener will be on the same level again. (He does not ask that the listener gain negative life experiences.) I don't think that "thief" is a good example of someone who has that earlier and lighter frame of mind that the speaker wishes to return to. The thief may be unafraid, but that mindset is probably not the solution that the speaker seeks from the "darkest place that you could be."

So, why use the word "thief" in "Thief"?

Answer 1

I'm not sure about any official meaning, and it's the first time I hear about this song, but it struck me like this:

So take me back

(to) When I believed

(So take me) Back when I was unafraid

(take me) Just like a thief

It seemed like "back" implied "taking", like in the first verse and the next line implies taking as well. As in thief isn't actually referring to the subject, but rather the one he's speaking to. Thief is one who's taking (well, could be back) things without asking, potentially at any cost.

The beginning of the next verse, i.e. "And" kinda ruins it. It could be substituted with an "of" in order to continue the "unafraid" line

(unafraid) And (?) Of all the heights

That I could reach

(So take me) Back when I was unafraid

(Take me) Just like a thief

Other possibility is he is recalling the heights he could reach back when he was unafraid and "Just like a thief" is a refrain of a kind, so it implies the same context as the first time, i.e. it's not a continuation of the previous line but stands for itself.