Answer:
they thought more colonies you have, the more powerful you are
Step-by-step explanation:
that was the main reaosn but there are other reasons aswell for example the british landed in surat in india in 1608 to trade and started trading in 1612
they were mere traders at first but then they wanted to increase the size of their empire and introduce their culture across the world since they thought that they had superior culture and were a superior race, similar was with other countries like the dutch first took hold of east indies' (modern day indonesia) trade but then conquered and colonized it to show other countrie show powerful they are
other reason include religion like portugal sent christian missionaries to convert the local population of their colonies