The core concept behind disruptive products are that they are better in some things but worse in many of the things provided by incumbents.
Incumbents react by dismissing such things as "niche" players.
The problem is that such perspective assumes a static view of the market. You’re assuming that all the other attributes of your implementation will remain advantaged and the new competitor will fail to translate that single advantage into a broader attack.
In a non-static market, everything changes.
... everything you ever did will get revisited in a new context with a new implementation even if it (a) means the use case goes unanswered for a while and (b) the execution ends up being slightly different.