Is there a specific reason why larger operators decide to run bus services before a smaller company's bus service because I don't find this particular fair and very intimidating because there is always the fear that larger operators will see that there is a smaller competitor running a service and then they will want to also run that service and will not want any competition from other operators
Examples of this issue occurring were with Stagecoach and multiple smaller operators in the South of England in the 90's and Southern Vectis with other operators at an unknown period of time
Yes, it's called competition and the free market.
As I mentioned in the other thread about London's buses, outside of the capital, services are run commercially. This means that bus companies are private business, with their revenue reliant on fare paying passengers. This is where the money that pays the drivers wages, the money that buys the buses, and the money that pays to keep the buses roadworthy comes from. It can be a real 'kick in the teeth' after you've spent all that money for someone else to come along trying to take your customers, no matter how big or small the rival business is. If they don't do something to address that the competition exists, then they'll start losing money. Look at any other market out there, and you will see businesses competing in one way or another for your custom precisely for this reason.
Obviously there can be questions asked about exactly how to deal with said competition. The tactics you described were one of many used in what were sensationally referred to as 'bus wars'. Other tactics included parking buses on stands to stop the rival from being able to stand and preventing access to bus station. I've heard of stories of rival buses racing through the streets of Oxford to be the first to pick up passengers and even tales of people setting fire to rival depots. In many of these cases, competition watchdogs and traffic commissioners have inevitably got involved, and companies are often left 'licking their wounds' afterwards. Obviously all the tactics in this paragraph do not benefit the passenger, and are frowned upon heavily. But even more seriously, some years back there was a fatal crash in involving a bus in Manchester. It was found that the driver of the bus had been encouraged to work way in excess of his legal hours, and the company involved (UK Buses, a newish company who were in a 'bus war' with Stagecoach) had altered documentation to try to hide this. The company had its operating licence withdrawn, and two directors went to jail.
However, I think many bus companies have moved on from the 'bus war' style tactics you've described (which in many cases have been ruled illegal), and instead now try to attract passengers through investment in newer and higher specification vehicles, offering a more comfortable and reliable service. In this instance, the passenger also benefits from the competitive market through lower fares and a better quality of service; and as such, competition does need to be encouraged.