Eclipse Execuition Protocol

[Aned]

I am trying to underestand the behaviour of running eclipse plugins.
what I did is I created a simple Hello World plugin using the the
provided wizared of Eclipse 3.2. this plugin contains two java classes
, one for the lifecycle(Activator.class) and the other one for the
action behaviour of the plugin (HelloWorld.class). In order to
underestand the order by whici Eclipse handle the plugin I wrote a
print statements in every method in both classes in order to see in
what order these methods are going to be invoked and what I found is
some thing like this:

Instance of HelloPlugin is created : Activator Class
This is the start method : Activator Class
Instance of the SampleAction is created : HelloWorld Class
This is the init method : HelloWorld Class
This is the SelectionChanged method : HelloWorld Class
This is the run method : HelloWorld Class
This is the dispose method : HelloWorld Class
This is the stop method : Activator Class

what I could not underestand is why eclipse has switched the running
procces this way? note that there is no relationship between the two
classes. Is there a standard running protocol that eclipse follows to
run its plugins?