[Concave]

I think there are a few plausible motivations:

A) Holo has more lowbies; they die a lot more easily to trains.
B) Holo had twice Az's numbers, so modulo a few assumptions the train was more likely to hit Holo than Az, most of the time.
C) Someone from Az called the fight 'obvious suicide' given the numbers on both sides; maybe Redd felt like the best way to take a chunk out've Holo was to force an ugly CR and/or wipe everyone and re-engage with C.R. gear / Azrael alts, while most of Holo'd be left naked.

The video's not incontrovertible evidence IMO but it is pretty persuasive. Hard to imagine how he collected more shrooms right after the first set that were on him hit everyone if he wasn't actively collecting them and dropping them on the fight.