I think you misunderstood Tre completely. he considered Simon as a very "good" friend. Tre asked Simon about Amstrad in the morning. Simon didn't say it is a job interview and every one is for himself!!! Instead, he started saying rediculous things like "Amstrad makes computers!!!". He is the one who behaved like a schoolboy not a man!!!
Simon won 5 tasks all of them were with Tre. When he was separated from Tre twice, he lost both of them. Simon was a PM twice and Tre gave him all the support he could afford. Even in the final task, if you see the previews, you can see that Tre is doing all he can for Simon to win the task.
Tre must have seen the program in the you're fired show for the first time. Simon didn't only refuse to give him information about amstrad, he laughed at Tre behind his back, and made sure that Kristina didn't give Tre anything either. You won't expect this from a "good" friend. Would you?