What did muslim leaders and scholars do to preserve and expand knowledge and learning

Muslim leaders built schools and libraries and also translated books to Arabic to help preserve and expand knowledge.

They kept all their knowledge written down and their language is still here today to decipher what they have said.so they could have more descriptive information.

They made a checks and balance system to equal power within the branches. the "check" meant that one branch would watch one branch and "balance" them if they were too powerful. if you want more info on this, i would just google checks and balance system.