It seems that forking the mother of all cryptos was something very doable.
It was always doable. It happened before. This time it happened during the scaling drama, so it got a lot of attention, even mainstream media were publishing sensationalist articles like "Bitcoin split in two, future uncertain".
Is there something stopping it from happening again and again in the future?
No, it's the nature of blockchain and open-source projects.
And how are mutliple forkings going to affect bitcoin?
In the long run - they are irrelevant, unless they somehow deliver better network than Bitcoin - but I don't see it happening in the near future (2-5 years).
Short-term effects of forks may vary from near-zero to somewhat distracting.