When the effort is no longer profitable...
Eh, only weakly connected if you ignore the telecomms all of them answer too, the FCC who oversees all of them to one degree or another and has a lot of former industry in it, or former FCC in the industry, the investor overlap (hello Blackrock/Blackstone/Vanguard pattsies), and the IC/State Dept ex-fed employee overlap.Firstly, this is why the term "Big Tech" is so useless for this kind of thing.
AFAIK major Software and Hardware vendors are not accused of any of the censorship or collusion with the Federal Government like the Social Media companies are. We call them all "Big Tech" but Microsoft and Facebook are in two completely different industries that really don't ever compete with each other. Likewise, say, Cisco and Twitter are both part of Big Tech, but are so separated it's like treating a Steel Mill that provides railroad as part of the same industry that publishes pamphlets that are read on train trips. Yes you could say they both are part of "Big Transit", but are in such completely unrelated areas of the market they don't even intersect.
So basically, no, I don't consider it a conflict of interest since you're talking about unrelated corners of a overly broad industry term. Secondly, at that point you're effectively nationalizing the industry and while the Federal government CAN TRY, what you're proposing is going to then have considerable legal costs as the courts work out things (and it's not sure things will go the same way, the WW2 and Korean War era court cases regarding industry nationalization are not favored by the current Supreme Court), plus it causes potential long term issues with those companies who might take this as a sign that it would be better to not work with the Federal government and so may no longer bid on Federal contracts if the government is going to pull such shenanigans.
Like I have been consistently saying, as presented this has potential to be overly broad and have unintended consequences. "Big Tech" is a highly nebulous term that applies to sections of an industry that are only weakly connected.
Sometimes you need to hit a broad target to make sure you've hit everything that needs hitting, particularly when more precise measures have consistently failed to handle the situation.