Like the first SE (and the far less successful iPhone 5C) this is an attempt to sell to a more price-sensitive market that wouldn't consider their flagships in the first place. It's also not exactly unique; Samsung has everything from 100 euro units to those folding phones that cost twice as much as an 11 Pro, say.
The original SE didn't noticeably cannibalise the flagships, and it was in some ways a more appealing device than this (it filled the "smaller" niche, whereas it's hard to see how this one is in any way better than an 11 Pro).
The first SE and the 5C were redesigned models. This version is unique in that it is not unique. Its a goddam rebrand of the iphone 8 sold at prices cheaper than any of the iphones ever.
5c was priced $649 for a 64 GB unlocked version.
The original SE didn't noticeably cannibalise the flagships, and it was in some ways a more appealing device than this (it filled the "smaller" niche, whereas it's hard to see how this one is in any way better than an 11 Pro).