Question

If the speed of light were the same in all materials, would a lens cause light rays to bend?

Answer 1

No.  If the speed of light were the same in all materials,
then a lens would NOT cause light rays to bend.

Also, here are a few additional tid-bits to consider
if the speed of light were the same in all materials:

-- The straw would not look 'broken' where it enters the water in the glass.

-- Cameras could not work.

-- Microscopes could not work.

-- Telescopes could not work.

-- A magnifying glass could not work.

-- Your EYES could not work.

-- Radio waves could not bend to follow the curve of the Earth.

-- A prism could not spread white light into its constituent colors.

-- Rainbows would not work.