Have a look at these. If you can afford to pay lawyers to set schemes up like this, then you are at a competitive advantage against businesses which pay regular tax.

https://en.wikipedia.org/wiki/Base_erosion_and_profit_shifti...

https://en.wikipedia.org/wiki/Double_Irish_arrangement

https://en.wikipedia.org/wiki/Dutch_Sandwich

Take the billions of dollars that you've saved from BEPS and use it to subsidize your local products, or run ads attacking the competition, or taking them to court, or hire salespeople, or build new content. Simple.

Several big-enough companies use tax loopholes to avoid paying taxes or lobby the government themselves.

This is not specific to big tech though, it's a single point of failure of having a centralised government that is easily corrupted by rich corporations.

sorry, again, I'm not following you. How does the ineffectiveness of tax regimes mean that Google and friends aren't competing like a normal business?

This reads like sealioning. You really can't see why an entity A that gives 1% in taxes is at an advantage in competing with an entity that gives say 20% in taxes?

but this behaviour (as said above) is not unique to tech. All sufficiently large, sufficiently multinational businesses effectively stop paying the full rate of tax