Might be stupid question but I want to know why only Spain and Portugal seemed to want to find other trade routes to Asia and why they led the age of exploration
Well if the question is earnest, then theres no such thing as a stupid question. Some related questions have already been asked and answered here and here. There are further discussions to be read on the overall subject page found here. If you have any followup questions that aren't answered, do feel free to ask but Im probably not gonna answer, as its not my field of expertise.
Edit: Automod made me aware that I should mention u/terminus-trantor, as he wrote the linked answers. To u/terminus-trantor I apologize for not doing so.