I'm going to go into my own speculation. Morton could have negotiated with McBain, found out he's eager to build a station, and worked to their mutual advantage. But that would go against the theme of the film. Negotiation, communication, and mutual benefit are never considered, never even raised. In Sergio Leone's westerns, problems are only solved by violence.
Sergio Leone's westerns were about subverting the black and white, good vs bad morality of American westerns. He presents the same basic stories, the same good vs bad framing, but the morality and motivations of his characters are more out of self-interest than "good". For example, in his "Dollars Trilogy", Clint Eastwood is presented as the "good guy". He's not particularly bad, but he's certainly not good. He's mostly in it for the money.
"Once Upon A Time In The West"'s "good guys" are all in it for themselves. Harmonica is not protecting Mrs. McBain, he uses her for revenge on Frank. Cheyenne, a murderous criminal, seems legitimately concerned for Mrs. McBain, but more out of boredom and curiosity than heroism. Once their interests are served, rather than riding off into the sunset, they abandon her.
The victims are the McBains. While their murder is heinous, the McBains are not presented as particularly sympathetic. Mr. McBain is in it for the money; for himself and his family. He's a harsh father who smacks his children and married a whore he hardly knows to raise them. Mrs. McBain, rather than a weeping widow, is literally a whore shown to be more concerned about her dead husband's money than her dead husband. She even considers forming a relationship with Frank, her husband's murderer, if that means saving herself.
Frank, the very bad guy, is a good looking, well dressed, smiling man. He's also a thug who kills children when it's convenient.
Morton, ostensibly Frank's boss, is a cripple barely able to control his underlings. Morton is obsessed with reaching the sea. His terminal illness is increasingly making him desperate, rushed, and willing to accept Frank's immoral methods as long as they solve his "little problems".
Harmonica, Cheyenne, Frank, Morton, and Mr. McBain all use violence and intimidation to solve their problems. Unlike the clean "good guy with a gun" ethos of American westerns, Sergio Leone's westerns show violence as brutal and amoral.
Morton needs McBain's land to build a station; McBain is in his way. We never hear about any attempts to negotiate with McBain, nor of McBain informing Morton about his intent to build a station. Instead, McBain keeps it a secret. That would require communication, mutual trust, and understanding. These all go against the theme of showing the nature of solving problems by violence: quick, brutal, decisive, efficient, and amoral violence.