We begin by acknowledging that “2” is not a real thing. It is an incomplete idea, a description, a modifier of real things. Two people are real; remove the people, and the number ceases to be. The people continue to be without the number, even when they are a divided pair of ones.
Then consider the number of things to which “2” can apply. Two people. Two battleships. Two bunches of grapes.
Consider also that “addition” is a floaty concept. If you move two bunches of grapes over next to two more bunches of grapes, you may well have four bunches of grapes. If two of the bunches grow tangled as you mush them together in a sloppier addition, they may well become three bunches of grapes. More common in my produce experience? You throw four bunches of grapes together, a few twigs snap, and one bunch breaks into two. This leaves you with five bunches of a grapes as the result of adding two and two.
Thereby, 2 + 2 = 5.