I have no idea if he lent on people - do you?
So why do you think MI6 suddenly withdrew their concerns about him? Do you think the committee wouldn't have doubts about appointing someone that MI6 has flagged as a potential threat?
Besides, it goes way beyond his peerage. Johnson has been very lax on Russia, almost to the point of being an apologist at times in the past. Although he has other links to Russia, both financial and personal.
On the annexation of Crimea, he pretty much blamed the EU just to point score in the Brexit debate.
He said we should work with the Russian's in Syria to support Assad, despite them being untrustworthy.
He has attended parties etc with Lebedev without his security detail, giving the KGB officer's son a chance to influence him, not to mention the donations from Russian sources to his own campaigns and the Tories in general where Russian individuals have had the chance to spend time with him and undoubtedly forward their own agendas. Or do you think they really wanted to play tennis with the fat oaf?
He's given huge loopholes in his sanctions on Russian oligarchs so they have the opportunity to secure their wealth before they take effect but let's it look like he's taking tough action.
if even a fraction of that had been done by Corbyn (or anyone in Labour for that matter) you'd be labeling them a security risk and a Russian agent.