I would have concerns with a 100 watt DC panel being able to handle a 65 watts AC swamp cooler. Conversion loss, motor startup current draw, etc.

Big alternating current fans that can move air do use lots of power. Especially a current surge at startup.

It sounds like in this space, people are making their own direct DC powered swamp coolers that are using less power, with relatively low flow fans. That's what I was missing.