This was an offence of criminal damage being reckless as to whether life was endangered. This is far more serious than simple damage to property.
The link is here. sentencingcouncil.org.uk/offences/crown…
This was a Category 2A offence. Starting point 6 years, a range of 4 years to 10 years.
Whether you agree that it is proportionate compared to how other offences are sentenced is a matter for you.
But there’s a lot of detail ignored by some of the noisier commenters.