Lavrynovych, who started the fires, was also convicted of being reckless as to whether life was endangered in relation to two attacks on May 11 and 12 that year.
The jury, which was presented with hundreds of pages of evidence, took seven and a half hours to reach a verdict.
Mr Justice Garnham remanded Lavrynovych and Carpiuc in custody to be sentenced on Friday.
The trial revealed that El Money had offered Lavrynovych £3,000 in cryptocurrency if the blazes were filmed and made the news.
During the trial, the prosecution urged the jury not to focus on who ordered the hit.
Prosecutor Duncan Atkinson KC said: “It is no part of your considerations to decide who ‘El Money’ is and what reason he might have had to co-ordinate the actions of these defendants against these properties and this car associated with the Prime Minister.”
But James Scobie KC, representing Lavrynovych, told the jury: “Let’s call it out.
“Russia are interested in what this country does in support of Ukraine.”
Referring to El Money, Mr Scobie said: “Where’s he from? Who might have an interest in trying to undermine this country, undermine this country’s support of Ukraine who are fighting for their liberty?
“Who might want to send a blow to the Prime Minister? Show him: ‘we know where you live’?”
“Their aim: publicity. And they got it. There’s one winner here, no doubt about that.”
Sown atmosphere of chaos
Kremlinologists say Vladimir Putin’s regime has sown an atmosphere of chaos which could have created the circumstances for a hit on the Prime Minister to be ordered.
Following Monday’s verdict, Commander Helen Flanagan, head of Counter Terrorism Policing London, said: “Crimes, such as arson, being directed by anonymous online accounts promising payment, is a recurring trend in our casework.
“Our message to anyone who might be approached in this way, or thinking about doing similar, is to think again. As we’ve seen here, you will not get paid as you are promised, you will be identified and brought to justice, and the only thing you will be left with is facing the prospect of a lengthy jail sentence.”
She added that while Lavrynovych and Carpiuc had not displayed an ideological motivation, “clearly the intention from the online tasker was to create fear, both for the victim and the Prime Minister, and cause uncertainty, unrest, for the UK”.
Some security sources also detect Russian handiwork in a conspiracy around the case that has spread rampantly online: that the defendants – young, aspiring models – were in fact aggrieved “rent boys”, who had torched Sir Keir Starmer’s home because they had not been paid.
The spurious claims stretch credulity, and are not borne out by the evidence presented in court, but the conspiracy has been promulgated far and wide online.
“The aspiring male model community seems to be particularly opposed to property owned by Sir Keir,” wrote one. “I think there’s a cover-up and Starmer has silenced the media,” wrote another.
Other security sources suggest the theory originated with Right-wing groups online, but note that Moscow is adept at amplifying theories that suit its agenda: sowing chaos and distrust.
A government spokesman said: “This was an abhorrent attack and those responsible have now been brought to justice for their acts. We thank our partners in law enforcement and the Crown Prosecution Service for bringing these criminals to justice.”
Kemi Badenoch, the Tory leader, said: “Keir Starmer and I disagree on many things, but good people across the political spectrum will welcome today’s verdicts, condemn these appalling attacks which seem to have been sponsored by Russia and wish the PM and his family well.
“Whatever our political differences, no-one should face intimidation, threats or attacks because they hold public office.
“Democracy is settled at the ballot box, not through fear or violence and definitely not through foreign interference from hostile countries.”