Why early carriers carried heavy guns

Did carriers other than Lexington carry guns, and why?

Many did, especially earlier carriers; their guns were intended for self-defence, not for deliberately seeking surface combat.

Carriers often carried significant batteries during the early carrier and interwar periods, when aircraft performance and doctrine were still developing. Some armoured Royal Navy carriers even came close enough to surface action for their captains to contemplate joining a battle line. That behaviour reflected the ships’ inherited guns and aggressive crews, not their intended operational role. The batteries existed for self-defence and did not justify employing a carrier like a cruiser or battleship.