They really have no defence either, they ran them on the route before the timetable change, some on the ground research would have told them changing the running times was a bad idea.
The same is true for almost every regional route though, Skegness for example appears to have had 5mins extracted from the timetable for the 80 odd miles. So where before you used to have a bit of padding especially around Grantham there's now none. Newark to Crewe seems to be similar.
Nothing except the timetable changed and punctuality went down across the board. We'll now spend the next 5 years coming up with grand ideas to restore punctuality until we get back to where we used to be, having achievable SRTs and padding to accommodate the unexpected.
A great example of what we used to have (maybe still do) was that Worksop to Nottingham used to have 4mins Mansfield Woodhouse to Mansfield Town. Turnbacks at Mansfield Woodhouse (MSW) had 3mins despite needing to accommodate a running brake test. This was due to the 3min SRT not being adequate so was extended to 4, but the entire WTT wouldn't work if the Woodhouse turnbacks had 4mins as that would have reduced the dwell at MSW which broke the plan.