I guess we’re about to find out because there is no good outcome for this convoy unless a lot of people want to get rid of Putin and sit on their hands when ordered to do various things to defend Moscow. And while it may be relatively easy to get near Moscow, as Napoleon and hitler found out, it is damned difficult to get into that city with much bigger forces than this convoy brings.
I think your pesimism is not justified. I give Prig a high chance of short term success if he crosses that last bridge into Moscow. If no one assassinates him, he has a chance of longer term success. It may depend somewhat on whether or not he has a secret deal with Putin or with Ukraine.