This is, in effect, the origin story of the "Kingsman" organization that we first saw in the very good "Kingsman: The Secret Service." (I see my review of that was ... well, not 100% positive. I've rewatched it several times and really enjoy it now.) The sequel ("The Golden Circle") kind of sucked. This prequel is a mess. It has a game central performance from Ralph Fiennes, and while it has a few fun action set pieces, it also has a couple others so improbable and ridiculous as to offset the good ones. It also felt very muddled as it mixed views of a life of privilege with World War I front-line drama and then switched to unlikely spy drama.
The biggest and stupidest plot hole (there are many, but this one out-gapes the others) is why anyone would choose to work for the bad guy, "The Shepherd." He's a James Bond villain, but at least James Bond villains appeared to pay their minions. This one expects loyalty to the death, and kills his associates whenever he gets pissed off. Yet they continue to do whatever stupid thing he says even knowing that. No explanation is ever given as to why these accomplished (if unpleasant) people would throw their lives away at the request of this insane maniac.