Time isinear because we decided it is, not because it is.
“Humans perceive three spatial dimensions: length, width, and depth. But mathematicians have long theorised there were more. In the 1880s, the mathematician Charles Hinton popularised these ideas, and went further. He didn’t just argue that space has a fourth dimension, he identified time with that dimension. Hinton argued that, because of the limitations of human consciousness, we perceive four-dimensional objects as changing three-dimensional objects. Yet reality is really an unchanging, four-dimensional space. What we perceive as time is misperceived space. The world is a ‘stupendous whole, wherein all that has ever come into being or will come co-exists’. Hinton doesn’t describe time as a line but, implicitly, describing time as a dimension of space means that, if time were taken by itself, it would be a line. Hinton’s work was speedily absorbed into the 19th-century air, and soon other 1880s thinkers were identifying the fourth dimension of space with time.”
https://aeon.co/essays/when-we-turned-time-into-a-line-we-reimagined-past-and-future