It is impossible to say exactly why the TVs died but you have to realize that they are built to be as cheap as possible and one of the ways that this is accomplished is to use parts that are so close to the minimum values that the designer specifies that they have very little margin of error. When the part ages or is stressed during normal use it fails more often. Capacitors in the power supplies are a major culprit. All brands have this problem but lower tier manufacturers such as Vizio are more prone to cost cutting. The no brand sets are even worse but even big brand names are cost cutting as much as possible. Be prepared for any TV to have a life of 4-5 years.
Your thoughts on increasing power problems is also true and make the above issues worse. Most power strips have very limited surge suppression and that wears out with time as each surge wears down the parts that suppress the surge.
They will need to be replaced over time. A whole house surge protector might be a good idea since you are also losing light bulbs. An electrician can install one at the electrical panel.