The entire game can be summed up by saying "Make the best with what you have every step of the way".
This is key to the replayability of the game and why this game remains playable and fun even as a computer game that is more than 15 years old. Every single game you will be thrown on your own resources and you will have to make the best with what you have every step of the way.
This underlying theme impacts every decision you will ever make when playing this game as long as you have not reached a point where the opponents are no longer threatening to you, at which time the game is effectively over and just needs to be brought to a close.
This is a game of galactic conquest, but make no mistake, the goal of conquest cannot be obtained without both a solid planetary infrastructure and a solid body of research.
This is the holy trinity of Master of Orion and what you must master to become the Master of Orion.
Mastery of Economy is the baseline for everything else that takes place in the game. Nothing can take place in the game at all without a solid production base.
A solid production base leads to resources that can be spent on research. This allows the player to stay on the same footing as the opponents and to hopefully pass them. One of the best ways to win tactical battles is through having more technologically advanced ships.
Only through mastery of the previous two phases of the game can the player hope to create a game winning galactic fleet and accomplish the objective of conquest.
Even if one tries to use diplomacy to win by a vote, they must often still proceed according to this plan.
If the player does not have the economy the opponents will out-expand them and the player will not be one of the two most populous races and therefore precluded from winning by vote.
If the player does not have strong research, they will not have (among other things) enough colonists per world to secure their place in the two most populous races. They will also not have the pollution reduction techs and other techs that allow significant portions of planetary budgets to be freely allocated to research.
If the player does not have a strong fleet, an opponent will see their weakened state and declare war in an attempt to increase their own relative power level in the game, both against the player and against the other computer players as well.