I think its a combination of both .
Older people who have been in it for many years have invested so much time and effort in it find it very hard to admit they have been wrong all those years.
In this case it is the investment of time and energy ,monetary value they have put in all those years that they cant back down and admit even to themselves that it is not the truth. So they keep deluding themselves.
And they keep defending it.
The other case I think is a different kettle of fish ,these people have gone out of their way to promote JW`s to all and sundry that Jehovahs Witnesses are the only true religion on the planet .
So their ego now gets in the way they have been so vocal promoting the JW religion and now they cannot go against what they have been so vocal for it would be humilliating for them to admit they have been so wrong..
So they keep deluding themselves.
And they keep on defending it
And as I said I believe it is a combination of the two indoctrination and insistence on being right that both parties can have a mixture of the two .