It literally states in the summary that when Sobble evolved it thought that it had managed to evolve into a Inteleon, but was disappointed when it’s saw it’s reflection and saw that it had become a Drizzile.Or the fact that it may have thought Drizzile would look good as a stepping stone but becoming one changed its mind.
So it’s pretty clear from the summary that Sobble thought it would evolve directly into Inteleon. Also it’s not hard to figure out that Sobble probably and likely thinks that Drizzile is a branch evolution and that Inteleon is forever out of it’s reach.
Because if Sobble knew that Drizzile was just a middle stage evolution that occurs before Inteleon then it wouldn’t have been depressed that it evolved into a Drizzle and would actually be happy instead because it would mean it’s half way to accomplishing it’s goal.
The fact that Sobble thought it would evolve directly into a Inteleon and got depressed when it saw that it became a Drizzile implies that it isn’t aware that Drizzile evolves into Inteleon nor was it aware that it would evolve into a Drizzile first.