Some points I’d like to address in your post.
Muhammad was not involved in violent wars. The Meccans based their economy on tributes to some 360 gods. When Muhammad proclaimed one God like Jesus and Abraham before Him the Meccans first tried to bribe Him by offering Him wealth and position to withdraw His stance. He refused. Then oppression and cruel persecution began against both Muhammad and His followers including murders. This went on for 13 years without retaliation. Eventually Muhammad and His followers fled to Abyssinia where a Christian king gave them Asylum. This infuriated the Meccans even more and their one aim and goal became genocide of the complete Muslim community.
Then they fled to Medina where the tribes had disputes they could not resolve and asked Muhammad to intervene. When He was able to unite them then they accepted Islam after hearing its message.
At that point Muhammad received this verse 2:190 from God.
2:190 And fight for the cause of God against those who fight against you: but commit not the injustice of attacking them first: God loveth not such injustice:
J M Rodwell
So from that point onwards Muslims were permitted to defend themselves but forbidden to attack unless attacked first. They were given the right to defend freedom of religion. And it was a case of being forced to fight or be destroyed. Muslims did not want to fight and this is recorded in the Quran too.
Innocent men women and children and those who did not attack or harm the Muslims were befriended and left alone.
2:62
Verily, they who believe (Muslims), and they who follow the Jewish religion, and the Christians, and the Sabeites whoever of these believeth in God and the last day, and doeth that which is right, shall have their reward with their Lord: fear shall not come upon them, neither shall they be grieved.
So the only people that Muslims were permitted to fight if attacked first were those who harmed them or broke their treaties and secretly worked with the Meccans.
Muhammad Himself never killed anyone in His entire lifetime.
After Muhammad passed away and left no will the Caliphs seized power and after a while desired to conquer for wealth and land but as the Quran forbade offensive warfare they fabricated Hadiths stating that Muhammad often went on killing sprees. This was a way for them to circumvent the laws of the Quran and get the people to follow them.
So from the death of Muhammad the Umayyads and Abbasids conquered and took lands but many people who were tired if Christianity infighting joined Islam willingly.
During the period when Christianity was in the dark ages, Islam established the centre of learning in Baghdad which drew scholars from all over the world.
Muhammad’s situation was different in that they had to resist genocide. They had no choice but to defend themselves or be wiped out.
But the conquests afterwards as with the Crusades witnessed both Muslims and Christians disobeying their own Holy Books and instead following blind egotistical leaders who were only interested in wealth and power not God or love anymore.
But today, most Muslims and Christians are peaceful people and so should not be judged on the wrongs of former generations.