>>58167430
Pokemon themselves are not a strategy, wide as an ocean, deep as a puddle. Most mons will fall into a strategy archetype and singles straight up has fewer archetypes.
The nature of having two Pokemon on the field means that there are more ways to support your team.
Imagine Raichu for a moment, I think it's a cool mon in lower power doubles formats. It has fake out support, electro web speed control, lightning rod is also good redirection to protect your other mon on the field.
What good is fake out and lightning rod in singles? Okay, you switch in Raichu for free and do some chip, but it's not like it's going to do much after whereas in doubles that's potentially a game winning move to protect your sweeper with redirection and then stall another turn with fake out.