Up until maybe 15 years ago, the news media used the word "pled" to describe what an alleged criminal had done in court to respond to the question if he were guilty or not, ie, "the thief pled guilty to the charge....".
In recent years you always read or hear that "the thief pleaded guilty to the charge....".
Why this change? You never hear the word "pled" any more.
It is a longstanding linguistic observation that irregular forms tend to become regular over time. Here is an interesting article on the phenomenon, and a predictive model that sprang from research at Harvand and MIT, specifically focused on the "regularization" of the irregular past-tense forms of verbs to forms with the -ed suffix.
"Before, language was considered too messy and difficult a system for mathematical study, but now we're able to successfully quantify an aspect of how language changes and develops."
Pleaded is not a new word. I always heard it growing up - over the last sixty plus years. It wasn't until I came to this country fifteen years ago that I heard it. Perhaps Pled is an Americanism and Pleaded is Queens English. I think they are two forms of the same word.