Perhaps it is an action boosting EU-based companies? Otherwise they are at a disadvantage in competition, because US-based Googles and Facebooks game the e.g. the tax system in a way that EU-based companies cannot.
Tax avoidance isn't helping large US based tech companies aquire more users or gain more control of the Internet. It only impacts investors and executives. So that's not the reason why EU based competitors have mostly failed to reach dominant positions.
No it doesn't really help. The money is mostly stockpiled offshore specifically to avoid taxation. They aren't using it to hire more employees or launch new products. The only thing it might help with is to prevent hostile acquisitions.
A) They have massive operations internationally and hire a lot.
B) Did you witness Microsofts dismantling of Nokia? That was a takedown of an entire ecosystem and huge gift to Apple and Google/Android as well. Paid for by cheap taxes overseas.