There would be no more rationale for assembly district than for state senate
district, congressional district, or school district that I can think of.

Here's the straight dope, from the California Elections Code:

13111. Candidates for each office shall be printed on the ballot in
accordance with the following rules:
(a) The names of presidential candidates...
(b) The names of the pairs of candidates for President and Vice
President...
(c) In the case of all other offices, the candidates for which are
to be voted on throughout the state, the Secretary of State shall
arrange the names of the candidates for the office in accordance with
the randomized alphabet as provided for in Section 13112 for the
First Assembly District. Thereafter, for each succeeding Assembly
district, the name appearing first in the last preceding Assembly
district shall be placed last, the order of the other names remaining
unchanged.

That doesn't mean there's any rationale for it; it's just the way it is.

I think that this is the best thing we can say about this little circus:
for those who are paying attention, there are some interesting civics
lessons, in a trivia contest sort of way.