Just to illustrate the logical error you are making here, which marks many of the argument made by Christian apologists: You are appealing to the supposed improbability of particular circumstances, but then suggest a literal impossibility as the solution. This is very poor thinking.
Let 's grant that it is highly improbable that the 11 would re-assemble after the death of their leader. I don’t really see what is so mind-bogglingly unlikely about that, TBH, but let’s grant that.
You now have to asses which is less probable: That 11 guys will get back together after having devoted their lives to following a leader after the death of that leader, or that this leader came back to life after being dead for 3 days.
I don’t see the algebra by which option 2 becomes clearly the more probable. Do you?