It is not self evident that layout optimization for typewriters dramatically differs from the optimization criteria for computer keyboards when typing English text. Even if you believe this it is not clear what the optimization criteria should be or whether or not any appreciable gains can be made over common layouts like Dvorak or Colemak.
I don't know what you consider to be "self evident". Clearly it is not apparent to many people choosing (or even designing) keyboard layouts, as this is commonly overlooked. However it is pretty straight-forward to understand if you spend some time thinking carefully about hand anatomy and typing motions.
Manual typewriters, between their invention in the 19th century and well past when the Dvorak layout was created, are very steeply angled, with a tall step between keys. It is relatively easy to reach up to the upper row from the home row, but a much bigger challenge to reach down to the lower row, especially for the middle fingers.
Most electronic typewriters / most desktop keyboards, along the lines of the IBM/Honeywell designs from the 1960s, make the lower rows easier to reach than they were on manual typewriters, but make it a bit (relatively) tougher to reach the upper rows because the step is not as aggressive.
Flat laptop keyboards (and other keyboards with uniform keycaps) exaggerate this. Reaching the upper rows requires either moving the whole hand or stretching out the fingers into a position that partially compromises the strength of the finger flexors used to type the keys. However, moving the fingertips one row closer to the body without moving the hand is relatively easy.
When typing several keys on different rows in quick succession, these features are amplified. (Many manual typewriters have the additional constraint that keys need to be pressed more rhythmically to avoid jamming, so "arpeggio" kinds of sequences are less relevant.)
The Dvorak layout optimizes for the manual typewriter design by only putting rare keys on the bottom row. The implicit key comfort cost function used for optimizing the layout is not really relevant on a modern keyboard.
(A simple summary describing whole rows is oversimplified; how reachable each key is from home position varies from key to key, finger to finger, and typist to typist. But it is a start.)