I don't think Qualcomm bought them to destroy them. I think they see Arduino as a gateway. Instead of hoping students will learn ARM it's more reasonable to leverage Arduino's simple nature to act as an on-ramp for more low level developers. I wouldn't be surprised if Arduino IDE saw a revamp to better support jumping the gap between the Arduino to Snapdragon.
ST and TI do the same thing with their boards too and it's not a bad strategy.
Some years back when bluepills ran $2, Arduinos seemed to have no point. Today, you can buy an ESP32 dev board with wifi for $6. Or an Arduino Uno Wifi for $55.
People are making so much of this when it seems so much simpler. Qualcomm likes buying high-margin businesses, and Arduino is a high-margin business. Gross margin on their boards is over 90% (hence why you can buy a Chinese clone of a $30 board for $3) and this trend shows no signs of slowing down. The TI equivalent of the $30 Arduino Uno is $5, and it's a true gateway product.