What 3 main decisions led to Brutus's downfall in Julius Caesar?

The first decision that led to Brutus' downfall is when he
decided that he would join the conspirators in their plot to kill Caesar. The plot did
not work. The conspirators had to flee for their very
lives.

The second decision that led to Brutus' downfall is
when he refused to listen to Cassius. Cassius warned Brutus to kill Antony along with
Caesar. Brutus did not want the conspirators to appear as butchers so he allowed Antony
to live.

The next decision that led to Brutus' downfall is
when he gave Antony permission to speak at Caesar's funeral. Again, Cassius warned
Brutus not to allow Antony to speak. Cassius feared that Antony would turn the people
against the conspirators, and that is exactly what happened. Brutus had to flee for his
life which ultimately led to his death.