Are companies more frequently flouting that or is this a case of suing companies while the regulatory framework catches up?
Basically, is suing companies to block acquisitions standard procedure?
As an example, in general the way Facebook and Google operate is not substantively different than it was a decade ago. The impending anti-trust action they are facing is a result of changing feelings and external conditions, not a (significant) change in law and regulation.
Google has always been an advertising company. Google's growing monopoly, however static their operating methods have been, is no longer viewed as in the consumers' best interest and is thus now under scrutiny.
I don't think it's all that accurate to frame this as "people in power are threatened by [big tech]'s power" when there are plenty of reasonable people making convincing arguments that big tech is no longer operating in the best interests of the consumer.
There are clear enough general goals and a factors to consider, I'd say. Those goals being that transactions are prevented based on if they are anti-competitive (limit competition in some way), and if the purchasing company has significant market power.
The sticking point though, is when those general goals are passed or not.
[0] https://en.wikipedia.org/wiki/Hart%E2%80%93Scott%E2%80%93Rod...
There are no rules that block any particular acquisition, just rules about whether you need to preemptively notify the government about the transaction and give them time to decide whether to challenge it.
https://en.m.wikipedia.org/wiki/Hart–Scott–Rodino_Antitrust_...