What is wrong with increases transaction speed and reduced cost?

What is wrong with increases transaction speed and reduced cost? 

There are a lot of comparisons of bitcoin fork with ethereum, but I can’t see any similarity except the forking. The arguments, logic, and reasons for splitting of ethereum were totally different irrespective of which side one may agree with.  I have been following the saga of bitcoin fork some the past few months and have not come across any convincing argument or reason why a large block size is bad or detrimental to bitcoin as a digital currency i.e. the sole purpose of bitcoin. I would greatly appreciate if someone could educate me by explaining the following questions:

I- Why do we have for SegWit to be implemented and wait for 3 months for the block size to be increased to 2MB? (I have read BIP 91 and I am not convinced). 

II- If increasing the block size to 8MB increases the transaction speed to seconds and reduces the transaction costs, then what is wrong with increasing the block size and avoiding the shenanigans we have been witnessing over the mast few month? 

III- Are there individuals or organizations with vested interest who want to control bitcoin and keep it under the cosh and keep the strings in their own hand? 

IV- Are there organizations and institutions who feel threatened by the success of decentralized blockchain currencies and hence keep throwing spanner in the works?