I have wondered this also. Coinbase clearly benefits from BTC and other cryptocurrency being "a thing", and rising prices help that happen. If the price of BTC that market watchers and news orgs quote is impacted heavily by the price on Coinbase, then their actions could have an outsize impact on the overall trend.

I would be curious to hear from folks savvier than me about suspicions like this.

EDIT: wondering why this is downvoted — I make a conjecture and then openly ask for perspectives of those who are more educated on these matters. If you disagree, responding would be helpful. We downvote things not because we disagree but because we think it doesn't add to the discourse.