Aluminum Electrolytic Capacitor Venting Creating Condensation in Enclosure
Yes, I've had old water-based electrolytics vent, releasing a small amount of both pure water, condensed from that which boiled off, and of spattered electrolyte. The spattered electrolyte is more conductive and somewhat more corrosive than the water, so must be cleaned thoroughly.

That said, most modern electrolytic capacitors are of the "dry" type, having little water content, so if you've noticed a lot of moisture, it likely came from somewhere else and preceded the demise of the caps.

Moisture could have caused failure both through corrosion or by providing a conductive path. For example, if two 400 VDC capacitors are in series, with parallel balancing resistors on the order of 100 kΩ, and moisture provides a path across one resistor, the PCB or one capacitor, it might cause 750 V to appear across the other capacitor, and 50 V across the "shorted" one. Worse yet, look for charring where the water provided a path for HV.