Conspirators make the worst post-planners when it comes to a unique situation. It is like all the effort has been on removing an obstacle you object to but then have no idea what to do next. Down with the tyrant! Long live err...who?
A situation like this happened in the Byzantine Empire in 713. A gang of soldiers had successfully deposed and blinded an emperor but had no leader to replace him. So as emperor Philippicus Bardanes bled all over the showers from his bloody eye sockets in the Hippodrome chariot racing track in Constantinople, his disfigurers argued over who should replace him. Another soldier-ruler or perhaps a civilian this time? Their choice fell on a civil servant by the name of Artemius Pyle got chosen. He had been Bardanes main secretary and diary keeper and also part time musician. Artemius initially refused as the previous four emperors had been executed and no one was giving Bardanes much chance to recover. But when you are surrounded by men who would kill you to move on to another candidate, he decided to accept. A change of name was also required. Artemius became Anastasius II.
Anastasius (we'll call him that from now on) was from a long family of quill ticklers in service to the Byzantine Imperial government. He was on the payroll and managed to steer out of trouble under his previous bosses. This future emperor gave no clue that he had any ambition. Anastasius married a local sweetheart called Irene and perhaps looked forward to a nice comfy pension when he retired, playing a few gigs with his band - a Byzantine version of Lynyrd Skynyrd. It was not to be. Anastasius became an emperor. One to put over his neighbours in the exclusive Bosphorus Sea View villas he had long lived on in a gated - and moated - community.
But then came the mutilation of Bardanes. The New Rome needed a saviour, so why not a fat civil servant and his boring wife to take that on? Anastasius became emperor.
Though no soldier, Anastasius was no chump either. In case those Byzantine soldiers who had killed his boss decided they were bored with him and wanted a new emperor? Anastasius neatly isolated the two men who he saw as a main ringleaders and had them blinded in turn. Bardanes may have been a crap emperor but there was a way to do these things.
The situation in the East began to look dire. Anastasius had no need for the new religious ideology either and banished Monothelitism from talk around the table. He wrote a letter of apology to Rome for the recent upheavals. Pope Constantine accepted Anastasius's diplomatic grovel and wheedled out some tax exemptions. A schism had been avoided.
Anastasius realised he needed to organise some handy victories to boost his popularity. He wasn't a general but decided he could pick 'winners' who could work for him. The enemies to hand with either the Bulgars or the Arabs. Since he had read all the reports under the previous emperor, Anastasius knew he had to prepare for something big from the Umayyad Caliphate, headquartered in Damascus. He would strike first. The Bulgars got some nice shiny presents if they stayed quiet.
A combined naval and military attack was planned. For the latter he promoted a promising and experienced soldier called Konon or perhaps 'Conan'. He became better known later as Emperor Leo the Iconoclast but was not at this stage breaking anything. The problem came from the navy. The sailors rebelled when the fleet was in Rhodes, killed Anastasius's commander and pointed their ships back towards Constantinople. On their way back to the capital the mutineers selected their own emperor, a charisma bypass called Theodosius III. He was a tax inspector and so like Anastasius, an imperial civil servant.
The rebel navy arrived outside Constantinople but there was no corresponding uprising in the city. It was going to be another siege. For the next six months the rival sides largely exchanged insults rather than a lot of arrows or other projectiles. Anastasius had already moved to the city of Nicaea with an army as he had expected Theodosius to arrive in that direction.
Anastasius perhaps hoped his friends the Bulgarians would intervene but they stayed at home. With the opposition staying strong, Anastasius opened communication with Theodosius to see if there was a deal to be had. There was. If Anastasius stepped down and resigned, he would keep his eyes and nose and any other extremity.
Anastasius carried on resisting Theodosius from his new makeshift capital but was finding it hard to recruit supporters. His star commander Konon/Leo the Iconoclast remained out East. So again Anastasius approached Theodosius for a 'new deal'. Theodosius confirmed the same conditions applied, though Anastasius would have to retire from public life and move to a monastery. His wife Irene would keep the villa. Anastasius reluctantly took the offer. In a humiliating ceremony he was divested of his imperial designer clothes and had them replaced with the Greek Orthodox Monastic Black.
Anastasius stayed in his monastery when the Arabic army and navy arrived to besiege Constantinople. By this time his successor Theodosius III had met the same fate as himself, consigned to a monastery (a different one) by the new emperor Leo the Iconoclast. Being a monk was no fun for Anastasius. Perhaps he could find a new ally? How about the Bulgarians?? He sent them a letter making promises if restored as emperor.
In the meantime Leo had won a great victory against the Arabic armies, helped by the Bulgarians. Perhaps one of them tipped off Leo that Anastasius was thinking about making a comeback. The former emperor bunked off from holy duties and headed towards the Bulgar kingdom. Anastasius managed to recruit an army of malcontents who had various beefs with Leo. But Leo was too quick. He arrived in strength before Anastasius could gather a bigger force. His troops deserted him and Anastasius was delivered in chains to Leo. Anastasius probably promised to 'be a good boy in future' but the grim Leo was in no mood to be generous. Anastasius was dragged away and beheaded. His widow Irene (who said her last goodbyes) was allowed to bury her husband's body. She kept the luxury villa.