Tepco has just publicly disclosed the video which captures Tsunami hit Fukushima Nuclear plant

Two months later after the incidents, Tokyo Denryoku (Tepco) newly  disclosed the video which captured how Tsunami hit the facility at Fukushima nuclear power plant.

The movie and picture shows Tsunami went over 10m seawall and went up to the top of  tank which hight was 5m.

But why did this disclosure have to be two months later?
Also, yesterday was the first date of the worker on site, went into the #3 reactor facility.

this is the video clip of the news show.
How Tsunami hit the facility shows up from 00:28 to 01:45.
http://www.fnn-news.com/news/headlines/articles/CONN00199726.html