You got it. It's alternating between too much and too little water. We can't help the too much water part when it rains like crazy but that's why a well drained raised bed helps alot especially in areas of wet summers. During dry times water deeply and wait for the top 2 inches of soil to dry out before watering again.

yes, too much water after too little leads to cracked, dead tomatoes(they turn before ripening naturally). Too little water after wet conditions leads to Blossom end Rot. Tomatoes need consistant conditions. I find that wetter conditions lead to bigger plants with more fruit but there are people who claim that dry consistant conditions lead to better tasting tomatoes. I don't know if that last one is true or not.

You can water less as the plant ages. Water more heavily in the early stages to help establish the plant, but then back off once the fruit is maturing.