The reason behind Blackberry’s failure was due to the company’s internal factors, like failing to cope with technological advances of competitors like Samsung and Apple, which captured market demand with modern and more attractive devices.
Examples were the Z7 and Z10 models which were irrelevant for consumers and way behind competitors products.

What this demonstrates s that big falls in demand to even bankruptcy can happen to any profitable and well known business globally. In this case was mainly due to the inability to progress with new ideas and advancements which brought blackberry back. Still technology might not be the only reason why companies may stay behind, as resources and costs are of big importance, but its a main factor of why companies take over their competitors. Another good example is Blockbuster in the industry of video cassettes, facing bankruptcy by not being able to cope with technological advances taken over by modern DVD’s.

Sources:

https://blogs.ubc.ca/vivekthakkar/2013/10/07/blackberry-in-doom/