The town was small, small population, so why not move the town a little higher? They clearly have huge government money just to observe the mountain, and they're rich with oil money.
Also, if that was such a big tourist attraction wouldn't there be dozens of towns in the path of the tsunami?
Also, with all the observation and analysis of the rock slide, isn't kind of obvious it's going to collapse soon?
The area is quite steep, so there isn't really a good place to "move the town to". And besides, there are many towns in the area that will be taken by this tsunami when it happens. It would be expensive to move all of them.
As for when it will collapse, it's hard to say. Maybe tomorrow. Maybe in 1000 years.
I think it's about 18 months ago another mountain was starting to slide. The geologists expected the slide to happen within days. And I think at some point the movement was up to more than a foot per hour. But then the slide stopped, and it stabilized. And the avalanche hasn't happened yet.
This goes to show that it's not so easy to know when it will happen. We only know that it will happen at some point.