After Jesus' death, there was a rumor that He was seen alive. The rumor spread very fast. The Roman imperial forces tried to dissipate the rumor utilizing multiple approaches from bribery to brutal force including death.
The rumor then spread to the capital of the Empire and Rome became Christian in a matter of years.
The reality is that all rumors, lies, and frauds are vulnerable to certain variables like time, complexity of the fraud, and the number of people involved.
For instance, the more people involved in the fraud, the more difficult it is to keep it together. But most importantly, no one gives his life for a lie and there were too many martyrs that gave their lives.
As time passes, rumors get weaker and weaker until people forget about it. Well, today there are 2 billion Christians that believe in that "rumor" that started 21 centuries ago… very strange! Isn't it?