Frankly, I find the responses to the post so far to be lacking a bit in detail. It seems the main response to why Ethiopia couldn't rapidly industrialize a la other communist states was because they were *too killpeopleist* to do so.
The Derg definitely did perpetrate an extreme amount of violence, but the reason they perpetrated this violence is the same reason they couldn't rapidly industrialize. Lack of control and legitimacy from the Derg (which fueled extremism) is the main reason that there was so much violence, and so the reason they could not industrialize as specified in the OP. The Derg came to power not through a highly organized and structured vanguard intending to seize power, but instead they realized Haile Selassie was weak and the imperial regime was completely rotted from the inside out. It quite literally blew over as slowly various sections of Ethiopian society started to push demands on the government. The Derg assumed command, and the most popular 'ideology' came from the students, and was some flavor of Marxism. In an attempt to posture and maintain control, the Derg (read now: Mengistu Haile Mariam and his clique) increasingly adopted the rhetoric of the opposition to its left. To simplify incredibly, this spiraled into infighting with student factions and leadership struggles within the Derg and the Red and White Terror kicked off which plunged the country into a very protracted and multi-stage civil war.
For most of its history, the Derg was fighting for control of the country, and in many places its ability to enforce policy (especially the former imperial peripheries) was tenuous as best. Of course, this fluctuated at different times and in different contexts, but remained very much a rule. For one of the best accounts of this first-hand, I highly recommend Donald Donham's "Marxist Modern: An Ethnographic History of the Ethiopian Revolution" which gives an account of the chiefdoms of Maale in southern Ethiopia and how they interacted with the center at Addis Ababa. The shifting web of local alliances with the state are crucial, but until the 1980s they primarily relied on evangelical Christians (!) to maintain state power, and after the anti-Evangelical turn (when Mengistu's regime appropriated Ethiopian Orthodoxy and the aesthetics of the Empire), they relied on the new WPE Party cadres but still faced rebellion and opposition from both Christians and Traditionalists. I think the book, alongside the constant violence and rebellions we saw IOTL, illustrate just how impossible it would be for any large scale economic construction to happen in Ethiopia during this time.