Siad Barre was incompetant, myopic and disastrous, although I do believe that in the first few years he was decent and making fast progress before he became corrupted (much more than SYL years) but the first big mistake he made was in 1973 oil market crises he was selling out to Saudi Arabia agreeing to their pleas that Somalia does not explore/exploit Oil, so oil price stays high in Saudi's favour. The second big mistake he made was becoming tribalist and betrayed Somalis he was a Daroodist (first with Marehan-Ogaden-Dhulbahante 'MOD' and then later last 5 years of rule it was Marehan-Dhulbahante-Majeerteen 'MDM').
The third mistake and the worst one of them all was deliberately botching the Galbeed/Ogaden war (which was not a mistake to actually start the war imo because Somalis in the galbeed were very opressed even although he personally had alterior motives which was to stay in power) because some of his cronies told him that when galbeed gets freed it will have negative effect on their grip of power, so Darood generals like Abdullahi Yusuf started the subversion of the Galbeed/Ogaden liberation war by invading oromo areas going outside of Somali inhabited areas which created furore in the world and thats when Russia, Cuba and North yemen came to Etiopia aid, people like Abdullahi Yusuf and Siad Barre knew what they were doing they were deliberately trying to lose the war, if the soldiers just holded onto the Somali inhabited areas of Ethiopia it would have been fair game and we could have called for a ceasefire.
The last mistake and the second worst of them all he made was the Isaac genocide.
I'm Surre so this critique is not coming from a position of cuqdad or envy like most others and is objective as we are not qabiilists we have history of giving sadaqa to many clans before our demise centuries ago.