If the fertilizer plant already blew up, why would you want to coax people out of their homes? The risk is past.
The most efficient emergency operations occur when they are using the regular economy.
If people are able to live in their homes, the last thing you want to do is to move them out.
Basic principle of Centralized command, decentralized control produces the most efficient and enduring social structures.
Well, we did say, "coax". Not 'force'.
I think you may be assuming that officials are looking to get people out of their homes who haven't been injured, have no property damage, and who aren't traumatized in any way. I don't think that's the case.
Also, the comment is now close to 24 hours old. Things have changed quite a bit on the scene since then. I'm sure that initially, officials simply didn't know whether there'd be more explosions, and just wanted people to evacuate the area for their safety.