The film was good but not killing anyone was their mistake
They planned it out really well but ultimately failed because of the minor flaws such as suspicious people who could rat them out and leaving the letter on the photocopier.
I know this is supposed to be based on a true story so I get why they didn't make too many changes, although I wouldn't know because I saw this at the cinema and what I knew before of it was the trailer.
By the way, it looked gorgeous in that huge screen, I guess that's what people call 4k or whatever. To be honest, I'm fine even with 720p quality.