Its interesting to see they had the contingency contract for McGann but not for Eccelston
They were made in different times and different contexts. The BBC didn't really make the TV movie and their approvals process for McGann was basically a rubber stamp. That was all down to Universal, which actually wanted to make a series (hence the contract) although FOX would only commit to airing a pilot. It didn't get the necessary ratings and so there wasn't a show.
When the BBC decided to relaunch the series in 2005, there wasn't a realistic expectation it would be a hit. Doctor Who was the butt of jokes. There was no family programming anywhere. Saturday had transformed from the jewel in its schedule to a ratings abyss. But it really wanted to work with Russell T Davies, who at the time was considered the cream of the crop in terms of drama scripting. He would only agree to come to the BBC for Doctor Who. The BBC agreed to one season, never expecting anything to come of it and assuming Davies would then produce the kind of drama he'd become famous for on other networks.
Davies knew an actor of Eccleston's caliber was required to give the relaunch credibility, and Eccleston's famous reticence to do series rather than serials worked in his favor since nobody really expected a hit. Davies was also clever enough to structure a season that could work as a self-contained unit while still allowing for a second season in the event the first was a hit.
It may be difficult for US viewers to understand this thinking five years later, but limiting the contract to one season opened up Doctor Who to a much higher caliber of actor. Bear in mind the BBC asked Hugh Grant first - and they could never have expected he'd come on for more than one season!
Speaking of, what about Martha Jones...why did she just last 1 year as a main character. Obviously she liked Who enough to guest in future episodes...I thought she was a great companion.
Martha is great. The plan there was always to keep the actress around for two seasons but the companion in the TARDIS for one. Davies was very open about this when he announced her stint on Torchwood and her guest role in series four. I think she did eight episodes that year, and with the way the production blocks work out this would all have been planned very early on. Davies was experimenting with the format. Some fans disliked Martha and started rumors she was fired, which is nonsense. Who hires someone for eight episodes after firing them?