Normally, with it (this is a dummy it), your expression should be followed by the conjunction that.
to happen as a result, or to be a likely result:
- [ + that ] Just because I agreed last time, it doesn't necessarily follow that I will again. (Cambridge)
With there, it is an idiom which means:
then comes : then there is
- The war ended. There followed a long
period of rebuilding. (M-W)
there follows something: There followed seven months of hard
The phrase there follows is often followed by a noun phrase, but it can also be followed by a that clause, and this use is more academic:
There follows that MoT = To (T- o MoT). There also follows that (MoT)o (MoT) o (MoT) = Moi...o M-2M or = Mo T. (source)
The conclusion is that both it and there are dummy subjects, but the main difference is
- It follows MUST be followed by that, whereas there follows can be followed by that or by a noun phrase.
- It follows that is not necessarily formal, and it is not restricted to academic writing. Especially in the negative or in questions, it is very common in colloquial contexts, too. There follows that is much more formal and is most likely to be found in an academic environment, particularly in the field of mathematics.