This is short term thinking. A slightly better Firefox tomorrow is nice I guess, buy I care way more about being able to use Firefox in 2030, or 2040. Making a browser is not looking like a business model that is going to make you last forever - not when Google is your competition. Their business model already depends on them being financed by other tech companies which are the epitomes of the ad tech industry. Their market share is shrinking, and the moment Google (and their other sponsors, but mostly Google) think they can get away with it they will cut Mozilla's funding.
I very much encourage their branching out if it leads to them being more independent and sustainable as a company. Moreover, I think [1] the idea of Firefox providing basic internet services is a really good idea.