It is difficult for the eye to follow very long lines of text, because when the eye has reached the far right end of the sentence it has to move all the way back and find the start of the line below it. This gets hard with long lines. Also, long lines of text look ugly. Print designers discovered all this centuries ago, and invented the text column.
If you right click a text box in PowerPoint and select format text, you see that one of the options you can choose is columns (Mac). Play around with the number of columns and the white space in between them to get the desired effect. As an example, below are the opening paragraphs of Alice in Wonderland.