Simplify the following text for a Grade 17 native English-speaking person.
Original: Galerius only discovered this when he received a letter from Constantine , who informed him of his father 's death , modestly asserted his natural claim to the succession , and respectfully lamented that the enthusiastic violence of his troops had not allowed him to obtain the Imperial purple in the regular and constitutional manner .
Simplified: Galerius only discovered this when he got a letter from Constantine , who told him of his father 's death , modestly asserted his natural claim to the succession , and respectfully lamented that the enthusiasm of his troops had not allowed him to get the Imperial purple in a regular manner .