michael adams wrote:

A better analogy may be two 3 metre diameter drums rotating on pivots
say 10 metres. apart. There's a large belt threaded around the outside
of the two drums, and a another belt threaded around two concentric
2 metre diameter drums attached to the larger drum. This makes the
circumferance of the large drum approx 9.3 metres and that of the
smaller drum approx 6.2 metres

Start off by drawing two vertical marks on the top two belts, say 1
metre from the left hand drum. Now rotate the left hand drum once
clockwise. The mark on the outside belt - the handrail will have
moved 9.3 m to the right
while that on the inner belt the - steps will have moved only 6.2 m.

I suspect this can all be explained quite clearly in two crisp
sentences by a competent engineer.

I'm not a competent engineer.... but how about

"You are talking rubbish. You are talking rubbish."

An escalator engineer was asked this question on TV. He said that when
escalators are new, there is no difference in speed. As components wear at
different rates, the speed difference appears.