Of all companies currently in the smartphone chipset game (which include Apple, Google and Unisoc), MediaTek was found to have shipped the most units in the last quarter of 2023 (4Q2023) and to have had one of the best rates of year-on-year (YoY) growth, with rivals such as Qualcomm and Samsung flat or flagging by comparison. Then again, the Taiwanese OEM was not the one that made the most money in that time.
From what I’ve read, they are considerably cheaper than Snapdragon. So entry level phones tend to use them more to keep the price of the phone down. Much like Nothing did with the 2a.