For someone with such an elite - and expensive - education, Johnson has a remarkable lack of class.
Johnson realises that he has managed to deflect from PartyGate with the Ukraine war only to be staring into the moral abyss of Tory party relationships with the Oligarchs. So he is doing the only thing he knows, which is to try to deflect. Everyone might be outraged now at such crass words from Johnson, but he is hoping that some of it sticks in the minds of the public and shifts critical focus from him and the Tory party to Labour.
The Oligarchs form an integral part of the Putin political and economic machine. Without them he would be unable to keep the control he asserts or launder the money that has made him very rich. One can split hairs on who is close to Putin, who has been critical etc. but the Oligarchs are an integral part of the Putin Kleptocracy. An Oligarch might speak out to certain extent against Putin, but if they aren't landing in jail or at the wrong end of some exotic poison then what they are doing is merely exercising the latitude afforded to them by Putin to retain plausible deniability of Putin's actions in orderto try to retain the freedoms in the West which allows them to launder the cash. They are like a dog that might bark but is careful not to strain any more on the master's leash than allowed.