The Lib Dems have zero credibility. Their headline policy in 2010 was No Increase in tuition fees, then they went and trebled fees anyway. Their other headline policy was voting reform which they allowed the Tories to sink.
In regards to the voting reform issue, you ought to remember that the Liberal Democrats had less than 10% of the seats at the time. They tried to give us an improved voting system, a compromise between what we have and what they wanted, and they failed. It was a pity, but hardly some cynical move by them.
As for the tuition fees issue, I think you may be guilty of reading a lot into the headline without really considering the detail. Yes, someone who goes to university now will indeed have a greater debt than someone who went to university prior to 2012. However, the new student loan is written off after thirty years and you the threshold beyond which you pay is greater, despite tuition fees being much higher. A significant number of people will pay less under the new system than they would under the old. Even those who will eventually pay more will initially pay less. I would be significantly better off (right now) if I had a new style loan. There are some major issues with the new student loan, but it is in many, many respects much more progressive than the old one.
I think student loans as a whole stink, and I think they should be scrapped. Yet being angry at the Liberal Democrats from being part of one pretty shit system evolving into another pretty shit system? It's just pointless.
Why would anyone trust the Lib Dems to do what they say in a manifesto?
Because frankly, this is politics, and if young people want to get anywhere, they need to stop waiting for perfection. The left desiring a messiah is the kind of shit that leads Donald Trump to being President of the United States. I'm not sure if you've realised, but the left is getting slaughtered. It's time to take some clues from the Conservatives and their voters and be little more pragmatic and a little less ideological.